Jazz Fingerboard Explorer — Upright Bass
Comping, walking and soloing all start from knowing the fingerboard: select a pitch and each EADG position that sounds it appears.
An interactive map of this seat's fingerboard in EADG: tap a note and it lights wherever it occurs, so 4 strings stop being 4 separate things to memorise.
Nothing marks these positions on the instrument itself, which is the whole difficulty — use this to see how far a shift actually travels before the ear has to make the same judgement unaided.
Every note a set of changes asks this seat for is already somewhere on this board; the changes pages only say which ones.