Xenharmonic Tunings
Any scale or tuning other than 12-tone equal temperament can be used to create xenharmonic music. This includes other equal divisions of the octave and scales based on extended just intonation.
Tunings derived from the overtones of physical objects with an inharmonic overtone series such as rods, prongs, plates, discs, spheroids and rocks are sometimes used as the basis of xenharmonic exploration. William Sethares is a pioneer in this area.
The Non-Pythagorean scale utilized by Robert Schneider of The Apples in Stereo, based on a sequence of logarithms, may also be considered xenharmonic.
Read more about this topic: Xenharmonic Music