D at the Piano Seat

Everything a chart can write over the letter D, in 10 families. Four or five of them carry most of the repertoire; the rest are what a reharmonisation reaches for when four or five stop being enough.

The piano seat carries the whole harmony at once — a shell in the left hand, the colour tones and any substitution in the right, which is why this is the seat a substitution is usually heard from first. It is the only seat here that can state a chord and its substitute in the same beat, left hand holding one and right hand implying the other.