Eighty-one ninth chords
Eighty-one 9th chords (2006) by Jacob Barton. For two pianos tuned to 17edo.
Recording
http://www.archive.org/download/seventeenTPP_02/81_ninth_chords.mp3
Score
Program Notes
1. "There are three types of thirds in 17-edo; let’s call them subminor (4/17-oct), neutral (5/17-oct), and supermajor (6/17-oct). If a ninth chord is composed of five notes separated by four thirds, then there are 3^4 = 81 of them in 17-edo. You will hear each of these once. Begin with the smallest — all subminor thirds — and end with the largest—all supermajor. The rhythm will help you keep track of the unfolding expansion. If you like the logic of this piece, I recommend the composer Tom Johnson."
2. "In Eighty-one ninth chords you will hear 81 ninth chords, each one a different type. I tried in the piece to let them be themselves but also connect them. Since composing it I read in Born on a Blue Day by Daniel Tammet (an autistic savant who sees and feels certain things when thinking about certain numbers) of nine as a number of particular immensity to him. This is exactly what it does here—phrases of length 2 or 8 feel even; 3 or 9 is ever a stretch."