Guitar chords in the key of Ab major

The seven chords of Ab major are Ab, Bbm, Cm, Db, Eb, Fm, Gdim. Each one has a job in the key, and each tends towards particular chords next.

• Ab, the tonic of Ab major. Usually goes to Db or Eb: the first move away from home, and the one that does not raise the stakes.
• Bbm, the supertonic of Ab major. Usually goes to Eb: roots falling a fifth, the strongest root motion the key has.
• Cm, the mediant of Ab major. Usually goes to Fm: roots falling a fifth, and vi is where iii most often lands. It contains the key's leading tone, so it leans towards the tonic.
• Db, the subdominant of Ab major. Usually goes to Eb: subdominant into dominant: the standard approach to a cadence.
• Eb, the dominant of Ab major. Usually goes to Ab: the tritone resolves: the leading tone rises, the seventh falls, and the phrase is over. It contains the key's leading tone, so it leans towards the tonic.
• Fm, the submediant of Ab major. Usually goes to Bbm or Eb: roots falling a fifth, straight into the standard approach to V.
• Gdim, the leading-tone chord of Ab major. Usually goes to Ab: it is V7 without its root, so it wants the tonic just as badly. The ♭5 puts a tritone inside the chord itself, so it cannot be sat on: it is heard as tension wherever it stands, and it is used on the way to something rather than as a place to arrive. It holds G and D♭, the tritone out of V7, so it carries the dominant's tension wherever it sits. It contains the key's leading tone, so it leans towards the tonic.

Where a chord tends to go follows Walter Piston’s table of usual root progressions in Harmony (W. W. Norton); see the sources.