Designed by Siemen Terpstra in the late 1980s, based on Erv Wilson's microtonal keyboard designs (1967-), inspired by R.H.M. Bosanquet's Generalised Keyboard (1873) and Ivo Salzinger's Tastatura Nova Perfecta (1721).
Initial development by James Fenn with additions and modifications from Brandon Lewis, Bo Constantinsen, Chengu Wang, Ashton Snelgrove. Sampling credits to Scott Thompson, Tim Kahn, Carlos Vaquero, Dr. Ozan Yarman, Lars Palo, Soni Musicae.
MIDI version designed and programmed by Marc Sabat. Current version 2.5 (2023), released as Free/Libre and Open Source Software under GPL-3.0. Code on github: https://github.com/000masa000/hexatone.