Eighty-one 9th chords (2006) by Jacob Barton
for two pianos tuned to 17edo
Program note from 1st performance (Seventeen Tone Piano Project Phase Two)
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.
Program note from second performance (Señor Recital)
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.
Update: new recording made with Pianoteq is featured on effluve ana moontense.