Long time microtonal composer/theorist/programmer. Got interested in overtone singing after hearing the Harmonic Choir in 1983 or so. Long associated with the American Festival of Microtonal Music.
My iOs app Droneo is a great way to hear and explore interval relationships, also online webapps like the Tone Spiral and the Lost Chord.
iOs devices, synthesizers, computers, hammered dulcimer, autoharps, flutes, free reeds, acoustic spaces like the Widow Jane Mine.
Partch, mathematics, Pauline Oliveros, Meredith Monk, the usual suspects.