The Key of F at the Upright Bass Seat

Called in F, a tune has F – Gm – Am – Bb – C – Dm – E° available to it before anybody substitutes anything; the parallel minor, F minor, offers Fm – G° – Ab – Bbm – Cm – Db – Eb instead. The two-five-one that closes most choruses is built out of three of those seven.

The upright seat carries the walk — one note a beat, the change announced on beat one and the three notes after it deciding where the next change came from. Almost none of a chord is playable this low and almost none of it is wanted: whichever note is at the bottom is the chord as far as the room is concerned, so the question is which note, and on which beat.

Learn where the ii, the V and the I fall in F until the hand goes there without asking, and the substitution rules become edits to something you already know rather than new material.