How to Play the A Minor 7 (Am7) Chord on Guitar

To play the A minor 7 (Am7) chord on guitar, mute the low E string, leave the A string open, press your middle finger on the 2nd fret of the D string, leave the G string open, press your index finger on the 1st fret of the B string, and leave the high E string open. Strum from the open A string down through the high E string. Two fingers, five ringing strings. Everything below covers exactly why each finger goes where it does, the fuller voicings and barre shapes that let you play Am7 anywhere on the neck, the mistake that quietly turns it back into a plain Am, and how to move into and out of it without stalling the song around it.

String names, numbers, and standard tuning

Every fret number and finger placement in this post refers to the six strings by both name and number, so it helps to have those straight first.

Strings are numbered thinnest to thickest, so the 1st string is the thinnest string, the high E, and the 6th string is the thickest, the low E. That numbering follows pitch, not the order your eye meets them when you look down at the neck, where the low E is usually the first string you notice.

Standard tuning, low to high, is E-A-D-G-B-E. Every fret and finger position described in this post assumes your guitar is in standard tuning. If your open strings are not producing those exact notes, none of the fret numbers below will land on the notes this chord needs, so it is worth checking your tuning before troubleshooting a shape that will not ring clean.

What notes make up Am7

Am7 is built from four notes: A (the root), C (the minor third), E (the perfect fifth), and G (the minor seventh). Stacked as a chord, that formula, root, minor third, fifth, minor seventh, is what defines any minor seventh chord, not just this one. Learn the pattern here and it transfers directly to Dm7, Em7, or Gm7 later, since they are all built the same way from their own root note.

The seventh is the note that gives the chord its character. A plain A minor triad (A, C, E) has a settled, resolved sound. Add the G, and the chord stops feeling finished, it leans forward, reaching toward whatever comes next rather than sitting still. That reaching quality is why Am7 shows up constantly as a chord you pass through on the way somewhere else, rather than one a song lands on and stays.

How Am7 shows up on a chord chart

Chord charts and songbooks abbreviate A minor 7th a few different ways, and it helps to recognize all of them as the same chord before you assume a symbol means something unfamiliar. "Am7", "Amin7", and "A-7" all refer to the identical chord described in this post, with the minus sign in "A-7" being jazz notation shorthand for "minor" rather than a subtraction of any kind. Some software and lead sheets also write it as "Ami7". None of these change the shape, the fingering, or the notes, they are just different house styles for writing the same four-note chord down.

The one symbol worth reading carefully is anything that adds a number or letter after the 7, such as Am7b5, Am9, or Amaj7. Those are related but distinct chords, covered later in this post, and treating them as interchangeable with plain Am7 will change what a passage sounds like even though the chord names look similar at a glance.

The open Am7 chord, string by string

Here is the full shape as a table. "Finger" uses standard numbering: 1 is your index finger, 2 is your middle finger, 3 is your ring finger, 4 is your pinky.

Build it from the two fretted notes. Your middle finger lands on the D string's 2nd fret, and your index finger lands on the B string's 1st fret, with nothing else to hold down. The A, G, and high E strings all ring open, and the low E string is left out of the chord entirely.

Every fretted or open string in this shape supplies one of Am7's four notes. The open A string is the root. The D string's 2nd fret gives you E, the fifth. The open G string gives you G, the minor seventh, and the B string's 1st fret gives you C, the minor third. The open high E string doubles the fifth. Nothing here is a wasted string, every string that rings is doing real harmonic work, even the two you are not fretting.

Am vs Am7: the one finger that changes everything

If you already know the standard open A minor chord, Am7 is a smaller change than it looks, and knowing exactly what that change is prevents the single most common mistake with this chord.

The only difference between Am and Am7 is the G string. In plain Am, your ring finger frets it at the 2nd fret, giving you A, doubling the root. In Am7, that same string is simply left open, giving you G, the minor seventh. Every other finger and every other string stays exactly where it already was.

This is also the most common way an Am7 quietly turns back into an Am without the player noticing. If you already have Am's shape built into muscle memory, your ring finger will sometimes drift back to the G string's 2nd fret out of habit even when you meant to play Am7, especially at speed. If an Am7 in a song is sounding a little too plain, too settled, check that G string first. Because the actual change is a finger lifting off rather than moving to a new spot, it is worth practicing the switch between the two shapes on its own until your hand stops defaulting to the more familiar one.

Which strings to strum and which to mute

Mute the low E string and strum from the open A string down through the high E string, five strings in total. The low E string does not belong to this shape, since Am7's root is on the open A string instead, one string higher than where a lot of players instinctively expect an "A" chord to start.

The most reliable way to keep the low E string quiet is aim rather than a dedicated muting technique, since your fretting hand is not close enough to it to rest against it the way it can with a chord that mutes a middle string. Start your downstroke at the A string and do not let the pick travel past it. If you strum all six strings out of habit, the open low E string will ring underneath the chord and blur its bass. A stray low E in particular clashes here, since E is not the root of this chord, and it will noticeably muddy the chord's low end even if every fretted note above it is clean.

Why your Am7 is buzzing or sounds dead

With only two fingers doing the work, there are two specific places anything can go wrong, and they tend to fail in predictable ways. Work through these one at a time rather than guessing at the fix.

Your index finger is too flat or too far from the fret

The B string's 1st fret needs your index fingertip coming down close to vertical, near the fret wire on the side closer to the guitar's body, not in the middle of the fret's open space and not lying flat across the string. Fret numbers count the space between two metal fret wires, not the wire itself, so a fingertip sitting in the middle of that space needs noticeably more pressure to avoid a buzz than one hugging the fret wire itself.

Move your fingertip until it sits just behind the 1st fret wire, then pick the B string on its own and listen. A cleanly placed finger next to the fret wire often rings out with barely any pressure at all.

Your middle finger is muting the G string

Because your middle finger's job is one fret higher than your index finger's, on a different string, it is easy for the side of that finger to lean back and brush against the open G string without you feeling it happen. Since the open G string carries the minor seventh, a muted G string quietly turns your Am7 back into a plain Am even though your fingers never moved.

Pick the open G string on its own while holding the rest of the shape. It should ring exactly as it does with no fingers on the neck at all. If it sounds shorter or duller than usual, arch your middle finger more so it comes down on its tip rather than its pad, giving the G string room to ring underneath it.

Your fretting hand is choking the open strings

With three open strings doing real work in this shape, the A, G, and high E strings, it is easy for the side of your hand, your palm, or a stray finger to rest against one of them without you noticing.

Pick the open A, G, and high E strings one at a time while the rest of the shape stays held. Every one of them should ring exactly as it does with your fretting hand off the guitar entirely. If any of them sounds shorter or duller than usual, adjust the angle of your hand or the position of your palm until every open string clears completely.

Not enough downward pressure

Even with good finger placement, both fretted notes need a minimum amount of downward force before they stop buzzing against the fret in front of them. New players often under-press simply because the specific muscles involved have not built the strength yet.

There is no shortcut here except repetition. Fret each note, pick it on its own, and listen. If it buzzes, add pressure gradually until it clears, then remember what that exact amount of pressure felt like, since you are training a specific amount of force into muscle memory, not just memorizing a shape.

Your ring finger has drifted back to the G string

Covered in detail in the Am versus Am7 comparison above, but worth repeating here because it is the single most common reason a new Am7 sounds wrong even though nothing looks obviously broken. If your ring finger lands on the G string's 2nd fret out of old Am habit, you have played Am, not Am7. Check that string first whenever the chord sounds a little too settled.

A fuller four-finger Am7 voicing

The two-finger shape above is a complete, correctly voiced Am7, not a simplified version you graduate out of. But once it feels solid, this alternative fills out the same chord with all four fingers, giving it a denser sound with the seventh voiced higher up rather than in the middle of the chord.

This voicing shares three fingers with the plain Am shape you may already know, index on the B string, middle on the D string, ring on the G string, then adds a fourth finger, your pinky, on the high E string's 3rd fret. That top note supplies G, the minor seventh, so the chord still contains all four Am7 tones, it just gets its seventh from the top of the shape instead of from an open G string. The root is doubled twice here, once from the open A string and once from the G string's 2nd fret, giving the chord a fuller, slightly brighter weight than the two-finger version.

Some players prefer this shape specifically because every string is fretted or intentionally open, none of it depends on an open string ringing exactly as long as the fretted notes around it, which matters more in a mix with other instruments than it does playing solo.

The Em7-shape barre chord at the 5th fret

Every open-position voicing above depends on open strings, which means it cannot move to a different key. This barre version fixes that by replacing the open notes with your index finger flattened across the neck, built on the same shape as an open Em7 chord and moved up until its root lands on A.

Lay your index finger flat across all six strings at the 5th fret, then place your ring finger on the A string's 7th fret. Strum all six strings, low E through high E, since every string in this shape belongs to the chord.

Worth being precise about here, because sources disagree: the extra note in this shape sits on the A string, not the D string. Some chord guides describe it the other way around, but working out the actual notes shows why that cannot be right, a D string fretted at the barre alone would produce a note outside the chord entirely. The A string's 7th fret is what supplies E, the fifth, on top of the four notes the barre itself already provides. If you have seen this shape described with the ring finger on the D string somewhere else, that is worth double-checking against your own ear before you build it into muscle memory.

This shape is movable. Slide the whole hand position up or down the neck and the barre fret becomes the new root, so the same finger pattern gives you any minor seventh chord rooted on the low E string, not just Am7, once you know which fret carries which note.

A compact D-shape voicing at the 7th fret

Further up the neck, a smaller four-string shape gives you the same chord without a barre at all, useful once a song calls for Am7 in a higher register or your hand wants a break from barring.

Your index finger takes the root on the D string's 7th fret, your ring and pinky fingers land together on the B and high E strings' 8th fret, and your middle finger reaches to the G string's 9th fret, one fret further up than its neighbors on either side. That last stretch is the part worth practicing slowly, since the G string sits between two strings fretted a semitone lower, which asks your middle finger to reach past where your hand expects it to land.

Strum only the top four strings, D through high E, and keep the low E and A strings muted or simply out of your strumming hand's path entirely.

Making the barre version easier on a smaller hand

The barre shape asks more of your hand than the open version, and a few adjustments make it noticeably more reachable rather than just a matter of pushing through discomfort.

Bring your fretting-hand thumb down lower on the back of the neck, closer to the middle, rather than letting it creep up over the top edge. A thumb positioned centrally behind your first and second fingers gives your hand more leverage to close the barre without your wrist bending at an awkward angle. Rotate your whole forearm slightly so your index finger approaches the strings from more of an angle rather than dead straight on, which lets the side of the finger, rather than its softest pad, do the pressing, and that side is naturally firmer.

If the barre still feels like a stretch, work on it as two separate motions before combining them: hold just the index finger's barre across all six strings on its own until it rings clean, then add the ring finger on top once the barre itself is solid. Trying to place both at once before the barre is dependable usually means the barre is the part that gives out first.

Am7 vs Am7b5, Amaj7, and Am6

Three other A-based chords look close enough to Am7 on a page to get confused with it, and each one is a genuinely different chord rather than a variation on Am7.

Am7b5, also called A half-diminished, flattens the fifth, replacing E with Eb. That single flattened fifth removes the stable interval that gives Am7 its grounded quality, replacing it with a dissonant tritone against the root. Am7b5 shows up almost exclusively as the ii chord leading into a V7 in a minor key, a specific jazz function that plain Am7 does not serve. Playing Am7 in its place removes that tension entirely and changes what the progression is doing.

Amaj7 is not a variation of Am7 at all, despite the similar name. Swapping the minor third for a major third and the minor seventh for a major seventh turns a reaching minor chord into a bright, unresolved major one, closer in mood to a warm daydream than the melancholy of Am7. Confusing the two on a chart, and they are easy to confuse by name alone, changes the entire feel of a passage.

Am6 replaces Am7's minor seventh (G) with a major sixth (F#), giving A, C, E, and F#. It has a brighter, jazzier lean than Am7's darker seventh, and it is a different chord entirely, not a simplified or extended version of Am7. Swapping one for the other changes the color of that moment in a song.

Am7 vs Am9

Am9 takes the full Am7 chord (A, C, E, G) and adds a ninth (B) on top. Every Am9 voicing contains an Am7 inside it, which is why Am9 chord shapes often look like an Am7 shape with one extra note added higher up. If an Am9 shape feels out of reach right now, playing the Am7 underneath it in the same spot in a progression is a reasonable simplification, since four of its five notes are already shared.

Where Am7 fits in a key

Am7 is not just a standalone shape, it shows up predictably inside several common keys, built naturally from the notes already in those keys' scales.

The G major row is the one worth knowing cold. In the key of G, the progression Am7, D7, Gmaj7 is the textbook example of a ii-V-I, one of the most common chord movements in Western music, jazz especially. The ii chord (Am7) creates gentle tension, the V chord (D7) increases it, and the I chord (Gmaj7) resolves it, a three-chord arc songwriters and jazz players return to constantly, whether or not they are thinking about roman numerals while they play it.

Knowing this does not change how you finger the chord, but it changes how you predict what is coming. If you see Am7 in a chart written in the key of G or C, there is a good chance a D7, G, or C chord is nearby, and you can start anticipating the shift with your fretting hand before the chart tells you to move.

The ii-V-I progression: Am7, D7, Gmaj7

This specific three-chord movement is common enough, and useful enough, to walk through on its own.

Play through the three chords slowly, one per bar, and listen to how each one leans toward the next. Am7 sounds unfinished on its own, like the first half of a sentence. D7 raises that tension further, since it contains a tritone that wants to resolve. Gmaj7 finally releases it, landing the progression back on solid ground. This three-chord arc is worth practicing in isolation, slowly, with a full stop between each chord at first, since it is one of the most transferable chord movements you can learn, showing up across jazz, soul, gospel, and plenty of pop written by musicians who learned their harmony from those traditions.

Common progressions built around Am7

Recognizing Am7 inside a real progression, and anticipating what is likely to come next, is what makes the shape useful once you are playing full songs rather than isolated chords.

If you already know C, G, F, and D7, learning Am7 alongside them fills in the missing piece of all three of these progressions at once, rather than being a new chord learned in isolation. Try playing through each row slowly, one chord per bar, and listen for how Am7 behaves differently depending on what surrounds it, resolving cleanly into Gmaj7 in the first row, adding a soulful lean in the second, and opening a turnaround in the third.

Changing into and out of Am7

The shape itself is rarely the hard part. The hard part is getting into it and out of it without a gap in the sound, and that depends entirely on which chord comes next.

Am7 to C

The standard open C chord uses your ring finger on the A string's 3rd fret, your middle finger on the D string's 2nd fret, and your index finger on the B string's 1st fret. Your index finger's B string position stays exactly where it was in Am7, so anchor that finger first and build the rest of the C shape around it.

Am7 to G

Standard open G places your middle finger on the low E string's 3rd fret, your index finger on the A string's 2nd fret, and your ring finger on the high E string's 3rd fret, with the D, G, and B strings open. None of Am7's finger positions carry over directly, so this change is really about speed and confidence in a fresh three-finger shape rather than reusing muscle memory from the chord before it.

Am7 to F

The standard open F chord barres the index finger across the B and high E strings at the 1st fret, then adds the middle finger on the G string's 2nd fret and the ring finger on the D string's 3rd fret. Your index finger's B string note stays in the same place, just extended into a two-string mini-barre, which makes this one of the smoother changes in this list, keep that finger anchored and build the rest of the shape from there.

Am7 to Dm

Standard open Dm places your index finger on the high E string's 1st fret, your ring finger on the B string's 3rd fret, and your middle finger on the G string's 2nd fret, with the low E and A strings muted. None of Am7's fingers carry over directly here either, but both chords share a similar overall hand shape low on the neck, which makes the change feel more natural once it is practiced than a first look at the finger chart suggests.

Am7 to E7

Standard open E7 places your middle finger on the D string's 2nd fret and your index finger on the G string's 1st fret, with the low E, A, B, and high E strings open. Am7's own D string note, middle finger, 2nd fret, is identical in E7, so anchor that finger and let your index finger swing over from the B string to the G string, one fret lower than where it started.

For all five of these changes, the same practice method works. Fret Am7, then the target chord, back and forth slowly with a full stop between each one, checking that every string rings clean before moving on. Only once that is reliable should you add rhythm, holding Am7 for a full bar and changing on the beat, gradually tightening the gap until there is none.

Where Am7 shows up in real music

Minor seventh chords like Am7 are especially common in jazz, soul, R&B, and funk, genres built around exactly the kind of gentle, unresolved tension a seventh adds to a plain minor triad. That is not a coincidence: the ii-V-I movement covered above is one of the most reused chord progressions in those styles, and Am7 is the textbook ii chord in the common key of G major and the vi chord in the even more common key of C major, so once you start listening for it, it turns up constantly in rhythm guitar parts, keyboard comping, and horn-section backing across those genres.

Folk and singer-songwriter guitar parts use Am7 often too, usually as a softer substitute for a plain Am in a verse that wants to feel like it is moving forward rather than settling. Because A minor is one of the most guitar-friendly keys, sharing all its open strings with plenty of other common open chords, Am7 tends to show up early for players working through folk, pop, and singer-songwriter songbooks, long before they meet it again later in a jazz or soul context.

Am7 and the A Dorian mode

Once the chord shape is solid, Am7 is also a natural entry point into the A Dorian mode, a scale lead guitarists reach for specifically over minor seventh chords because every note in it is either a chord tone or a smooth passing note against Am7.

A Dorian shares six of its seven notes with the A natural minor scale, and differs by exactly one note: where natural minor flattens the sixth to F, Dorian keeps it natural, as F#. That single raised sixth is what gives Dorian its brighter, slightly more open character compared to a plain natural minor scale, and it is worth noticing that F# is also the note that gives D7 its major third, the same D7 that follows Am7 in the ii-V-I progression above, which is part of why that particular chord movement sits so naturally under a Dorian line. This is a scale to come back to once the chord shapes above feel comfortable, rather than something to tackle at the same time as learning the chord itself.

Am7 and the A minor pentatonic scale

Am7 also connects directly to the A minor pentatonic scale, the five-note scale most players reach for first when soloing in a minor key.

Every note in Am7 is also a note in the A minor pentatonic scale. The scale adds one extra note on top, D, as a passing tone between C and E, but nothing in the chord sits outside the scale and nothing in the scale clashes with the chord. That overlap is why a solo built from the A minor pentatonic scale sits so naturally over an Am7 chord or over the ii-V-I progression above once the D7 resolves back to Gmaj7, an A minor pentatonic line will still land on chord tones far more often than not, since three of Am7's four notes anchor the scale's most common box shape. This is worth exploring once the chord itself is comfortable, using the chord to find your ear's way around the scale rather than the other way around.

Fingerpicking Am7

Because every note in the open Am7 shape belongs to the chord, it is a solid chord for practicing basic fingerpicking, provided your thumb stays off the low E string, which is not part of it.

A simple starting pattern uses your thumb (T) for the open A string and your index (I), middle (M), and ring (R) fingers for the D, G, and B strings, with your pinky picking up the high E string.

Play the open A string alone on the first beat, then roll up through the D, G, B, and high E strings one at a time. Keep your thumb anchored to the A string only, resisting the pull to drift down onto the low E string out of old habit from other open chords that do use it.

Once that basic roll feels steady, try breaking the pattern up: thumb on the A string, then straight to the high E and B strings before filling in the D and G strings on the way back down. Because every string in this shape is either a chord tone or correctly muted, there is no wrong note to land on inside it, making it a safe shape to experiment with different picking orders on before trying the same experiments on a chord with more strings to keep track of.

Am7 on acoustic vs electric guitar

The shape does not change between instruments, but how it behaves does, and it is worth knowing what to expect before assuming something is wrong with your playing rather than with the instrument's natural character.

On an acoustic guitar, the open A string rings loudly and for a long time, giving the open Am7 shape a warm, resonant low end that anchors the chord without you needing to do anything extra with your picking or strumming hand. On an electric guitar, especially with any amount of gain or distortion, that same open string behaves differently. Overdrive makes it ring out more aggressively and picks up unwanted noise from the muted low E string far more readily than a clean acoustic tone does, so pay closer attention to keeping that string muted between strums when playing through a distorted amp.

Clean electric tone sits closer to acoustic in how forgiving it is, though without an acoustic's natural volume and sustain from the body and soundhole, a clean electric Am7 can sound comparatively thin unless you lean into the barre voicing from earlier in this post.

Common mistakes beyond buzzing

A few habits show up specifically with Am7 that are not really about buzzing or muted strings, but about how the chord gets used.

Strumming the low E string out of habit. Because so many other open chords, including plain Am itself, are sometimes strummed loosely across all six strings, some players carry that habit into Am7 and catch the low E string anyway. Double-check your strumming hand is actually starting at the A string.

Reverting to Am's ring finger. As covered earlier, the single most common mistake with this chord is the G string drifting back to the 2nd fret with the ring finger, out of muscle memory from plain Am, especially on fast changes. If an Am7 sounds a little too settled, check that finger first.

Confusing it with Am7b5, Amaj7, or Am6 from a chart. Covered in detail above, but worth repeating: read the chord symbol carefully rather than assuming any A minor chord with extra letters after it is close enough to Am7 to substitute freely, since Am7b5 and Amaj7 in particular change the chord's function and mood entirely.

Treating the barre version as strictly better. The open shape is not a beginner shortcut you graduate out of. It is a complete, correctly voiced Am7 that many working guitarists use by default because it needs less movement to reach from nearby open chords. Reach for the barre version because a song needs that register or that movability, not because the open shape is somehow incomplete.

A practice routine for today

Fifteen minutes is enough to make real progress on this chord if you spend it deliberately rather than strumming through a song on repeat.

1. Five minutes on the shape alone. Fret the open Am7, strum from the A string down through the high E string, and listen for any string that sounds muted or buzzed. Isolate and fix it using the causes listed earlier in this post before moving on.
2. Five minutes on one transition. Pick a single change, Am7 to F is a good place to start since the index finger barely moves, and repeat it slowly with a full stop between chords. Once ten changes in a row ring clean, add a metronome at a slow tempo and change on the beat.
3. Five minutes on the ii-V-I progression. Play through Am7, D7, Gmaj7 slowly, one chord per bar, focusing on landing each change cleanly rather than on speed.

Repeat this same fifteen minutes for a few days before adding the barre version or a second transition. Progress on a chord like this comes from consistency across several short sessions, not from one long session where your hand gets tired and your form starts to slip.

FAQ

Is Am7 easier than Am? For most players, yes. Am7 uses one fewer finger than the standard open Am, since the ring finger that frets the G string in Am is simply lifted off in Am7. Fewer fingers fretting means fewer places for something to go wrong.

Can I use Am7 instead of Am anywhere in a song? Often, but not always. They share three of four notes, so they usually sound fine swapped in, but the added seventh changes how the chord pulls toward whatever comes next, so a chart that specifically calls for Am rather than Am7 is sometimes making a deliberate choice about that pull.

Why does my Am7 sound the same as my Am? This almost always means your ring finger has drifted back onto the G string's 2nd fret out of habit from plain Am, instead of leaving that string open. Check that finger position first, covered in detail in the comparison section above.

What is the difference between Am7 and A7? They share the same minor seventh interval, but Am7 is built from a minor triad (A, C, E) with a minor seventh added, while A7 is built from a major triad (A, C#, E) with a minor seventh added. The C versus C# is the difference between a minor chord and a major one, so despite the similar names, Am7 and A7 sound distinctly different, one darker and one brighter.

Do I need to barre Am7 to play it in other keys? Only if you specifically want the same voicing moved to a different root. If you just need a minor seventh chord somewhere else on the neck, it is often easier to learn that chord's own open or barre shape rather than transposing Am7's shape by ear.

Does Am7 still use the same fingering with a capo on? Yes. A capo shifts every open chord's pitch up without changing the shape your fretting hand makes, so Am7 played with a capo on any fret still uses the same finger and fret positions described in this post, it just sounds higher than it would without the capo.

Does Am7 sound different on acoustic versus electric guitar? Yes, though the shape and fingering stay identical. Acoustic guitars give the open A string in Am7 a warm, resonant sustain, while electric guitars, especially with gain or distortion, need more careful muting of the low E string between strums to avoid unwanted noise from a string that is not part of the chord.

Is Am7 a major or minor chord? Minor. It is built from an A minor triad (A, C, E) with a minor seventh (G) added on top. The word "minor" in its name refers to that underlying triad, and the seventh does not change the chord's fundamental minor quality, it only adds the reaching, unresolved character discussed earlier in this post.

How do I stop my hand from cramping while holding Am7? Cramping in this chord usually comes from unnecessary tension in the fingers that are not fretting anything, or from squeezing your thumb too hard against the back of the neck. Relax the fingers you are not using, and check that your thumb is providing light support rather than gripping.

Is Am7 the same as C6? In terms of notes, yes. Am7 (A, C, E, G) and C6 (C, E, G, A) contain exactly the same four notes, just thought of as starting from a different root. Which name you use depends on context: call it Am7 when A is functioning as the chord reaching toward resolution, as it does in a ii or vi chord, and call it C6 when C is functioning as a settled, resolved tonic. The shape on the neck does not have to change, only the chord symbol and how you think about its function within the progression.

Why do some chord charts show Am7 as a barre and others as an open shape? Both are correct voicings of the same four notes, just arranged differently across the strings and, in the barre version, movable to other keys. Charts aimed at beginners tend to show the open shape first because it needs less stretch, while charts covering movable shapes show the barre version because it works in any key without relearning a new fingering.