Spectra’s Mystery refers to the tuning devised by Michael Sheiman. Michael’s goal was: “Inspired by how 12EDO mysterious has ratios in between both 9/5-16/9 and 10/7-7/5 (guessing that may have something to do with how is sounds so harmonic despite its high error), I came up with an idea to find a “midpoint-based” scale ”
Spectra’s Mysterious Ratios
As for the “tuning unheard” improvisation. At about 2:30 you can hear the keyboard fall off the stand. I catch it though and the artifact is a fat finger cluster on the low end. About the piece overall. I open with playing the tuning to give you the gamut of pitches, start out slow and then try to push my limits and hit a flurry of bad notes and slow to close. I found the tuning to be pretty interesting and opened up more and more as I played it. Scala file and midi file of the performance for your enjoyment.