Guitar chords in the key of D major

The seven chords of D major are D, Em, F#m, G, A, Bm, C#dim. Each one has a job in the key, and each tends towards particular chords next.

• D, the tonic of D major. Usually goes to G or A: the first move away from home, and the one that does not raise the stakes.
• Em, the supertonic of D major. Usually goes to A: roots falling a fifth, the strongest root motion the key has.
• F#m, the mediant of D major. Usually goes to Bm: 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.
• G, the subdominant of D major. Usually goes to A: subdominant into dominant: the standard approach to a cadence.
• A, the dominant of D major. Usually goes to D: 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.
• Bm, the submediant of D major. Usually goes to Em or A: roots falling a fifth, straight into the standard approach to V.
• C#dim, the leading-tone chord of D major. Usually goes to D: 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 C♯ and G, 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.