Isomorphic Instruments

The instruments listed here and on the websites linked below follow the principle of isomorphism, the identical or similar appearance of intervals in all transpositions. This means they are key-neutral and scale-neutral. Isomorphism is also found in many alternative notation systems.


Intuitive Instruments for Improvisers (Paul Hirsh) –  A website about isomorphic instruments, isomorphic panpipes, Janko keyboards, and more…

Keyboards, Accordions, Button Instruments


The DIY Keyboard Project (Drew Wagner) –  Focuses on building alternative, isomorphic keyboards. It is an open-source hardware development project with the goal of making all of the CAD files, microcontroller code, etc. necessary for a hobbyist to build a digital keyboard freely available.

AltKeyboards website on isomorphic keyboards, focusing on the Wicki-Hayden note layout (Ken Rushton) –

Musix for iPad – One of the layouts is the Wicki-Hayden.

Single Row of Keys (Chromatic Scale)

Robbins Keyboard –

Dodeka Keyboard –

Multiple Rows of Keys (Chromatic Scales, Offset by a Perfect Fourth)

LinnStrument (chromatic scales a perfect fourth apart, reminiscent of a fretted string instrument) –

Two Rows of Keys (Whole-Tone Scales, Offset by a Semitone)

Symmetrical Keyboard (Dominique Waller) –

The Balanced Keyboard (Bart Willemse) –

Multiple Rows of Keys (Duplicated Rows of Whole-Tone Scales, Offset by a Semitone)

Janko Keyboard Layout

Daskin brand Janko Keyboards (Paul Vandervoort) –

Lippens keyboard derived from Janko’s design

Chromatone brand Janko-style keyboards (Japanese company) –

Chromatone Lite for iPad –

Multiple Rows of Keys (Whole-Tone Scales, Offset by a Perfect Fourth or Fifth)

Wicki-Hayden is a hexagonal layout in which odd-numbered rows are not duplicated as in Janko but instead are separated by octaves, as are even-numbered rows.  MNP Wiki page on Wicki-Hayden Layout

The Array Musicboard (Bill Wesley) uses a layout closely related to Wicki-Hayden –

Multiple Rows of Keys (Series of Minor Thirds, Offset by a Semitone or Whole Step)

Chromatic Button Accordions –

Multiple Rows of Keys (Series of Perfect Fifths, Offset by a Minor or Major Third)

The Tonnetz is a hexagonal grid in which the three diagonals are intervals of a perfect fifth, major third, and minor third.  One example is C-thru music’s “Axis” instruments using the “harmonic table” note layout –

Microtonal Keyboards

Generalized keyboard, a predecessor of the Janko keyboard that accommodates microtonal tunings (invented by R. H. M. Bosanquet, extended by Erv Wilson and others) – ,

Microtonal keyboards, including isomorphic keyboards –

6-6 Colored Traditional (7-5) Keyboard (on this wiki)

(Strictly speaking, this is not an isomorphic instrument, because only the coloring, not the physical layout, is isomorphic.)


Isomorphic Saxophones and Flutes (Jim Schmidt) –

String Instruments

Many traditional string instruments are isomorphic in their usual tunings (violin, viola, cello, double bass, mandolin, bass guitar). The guitar is mostly isomorphic in its usual tuning, with the exception being the major third between the G and B strings. Some people tune the guitar with all neighboring strings a major third apart, or all a perfect fourth apart, making the tuning completely isomorphic. Wikipedia page on regular tunings for guitar

The Harpejji, a fretted string instrument whose strings are tuned a whole tone apart, making it like a combination of a Janko keyboard and an electric guitar. – Page

Chromatic harp (strings arranged in whole-tone scales) – (Page in German)

The Array Guitar,  Psaltery, and Vina (Bill Wesley) –

Percussion Instruments

Isomorphic Vibraphone whose bars are arranged in whole-tone scales and have a three-color pattern (Roy Pertchik) – see Tri-Chromatic Keyboard Pattern

The Array Mbira, Nail Violin, Rasp, etc. (Bill Wesley) –