Harpejji

The Harpejji (see Wikipedia) is a tapping stringed instrument which is a physically constrained to be an isomorphic keyboard. It is a successor to the StarrBoard which was created by John Starrett.

The standard layout for a Harpejji is like this, with the open strings tuned in whole tones of 12edo, so that the seventh string is an octave above the first.

E  F# G# Bb c  d  e  f# g# bb c' d'
Eb F  G  A  B  c# eb f  g  a  b  c#'
D  E  F# G# Bb c  d  e  f# g# bb c'
C# Eb F  G  A  B  c# eb f  g  a  b
C  D  E  F# G# Bb c  d  e  f# g# bb

However, the same general idea for a layout can also be applied to any chain-of-fifths EDO, and the only difference is what shape the unisons take on the fretboard. (For a rank-2 chain-of-fifths tuning which is not an EDO, there will be no unisons on different strings).

For example, a 19edo Harpejji layout might look like this:

F  G  A  B  c# d# e# gb ab bb c' d'
E  F# G# A# cb db eb f  g  a  b  c#'
D# E# Gb Ab Bb c  d  e  f# g# a# cb'
Db Eb F  G  A  B  c# d# e# gb ab bb
C  D  E  F# G# A# cb db eb f  g  a

To interpret this, keep in mind that C-D is 3 steps of 19edo, E-F is 2 steps, and # and b modify pitches by 1 step. Thus there is a consistent spacing of 3 steps between adjacent strings (columns), and adjacent frets (rows) are 2 steps apart. (In contrast to 12edo, G#-Ab is not a unison but E#-Fb is.)

As you can see, the (meantone) diatonic scale has exactly the same shape on the fretboard, and the main difference compared to the 12edo layout is that unisons are no longer a knights-move away on adjacent strings (2 up and 1 left). Instead, in 19edo the unisons are 3 up and 2 left.