sfSound's Microfestival of Contemporary Piano Music: Chris Brown's 6Primes

Chris Brown performs 6Primes, his new suite for piano solo in 13-limit just intonation. sfSound members perform Brown’s Ragamala Chiaroscuro (2004), a tuning-based trio based on an evolving chord. 
Of 6Primes, Chris Brown writes:
“6Primes is composed using the six prime numbers 2, 3, 5, 7, 11, and 13 to govern both the tuning and rhythmic structure of the music, including the harmony and rhythmic subdivisions of the beat. The piano must be retuned in just intonation using the tuning system provided, in which the notes are tuned to one ratio with the highest prime factor of 2, three ratios with highest prime of 3, and two ratios each with highest primes of 5, 7, 11 and 13. The main feature of such a tuning is the diversity of interval relationships it creates: whereas 12 tone equal temperament has just twelve distinct intervals, this 12 tone system has 75. Most just systems do not use prime number ratios that exceed 7, since ratios using 11 and 13 are quite remote to learn to hear and tune. I wrote this music specifically to investigate the frontiers of what integer relationships are possible to hear and use melodically and harmonically; and simultaneously, what integer relationships are possible to play as rhythms. My conclusion after writing and practice it is that the level of difficulty increases at about the same rate for rhythmic relations as it does for pitch relations – and as the difficulty increases with each higher prime relation, playing them accurately is still possible, and new musical experiences are to be had! And while it does not seem possible to recognize intuitively the affinity of a rhythmic ratio relation to a corresponding pitch interval, since they are actually experiences defined by the same proportions, one can learn to appreciate their natural congruence. These experiences were pioneered in the music of Henry Cowell, which was played both by adventurous performers and by his Rhythmicon machine. In learning to play this music today, computer notation software is also very helpful! 
To find my way through these complexities, I made six pieces that each work with just four prime ratios at a time, thus creating a set of modes to compose in. The titles of each piece states these primes, although 2 is always represented as 4, and 3 most often as 6. Each piece is also structured into sections that use all possible combinations of 2, 3, or 4 ratios at a time for its pitch and rhythmic material. The measure length of each section is also equal to the sum of the primes it uses. Thus each section has its own modal quality that is a subset of the piece’s mode. The aesthetic goal was to be able to listen to and play all of the possible relationships within each piece, each for more or less an equal amount of time. The entire set of six pieces thus explores all 75 ratios quite thoroughly. I hope that like so much music that has come before it, it is enjoyable with or without an understanding of what number principles lie behind it!”
Starting the concert, sfSound members John Ingle (alto saxophone), Matt Ingalls (bass clarinet), and Kyle Bruckmann (oboe) perform Ragamala Chiaroscuro (2004), a tuning-based trio based on an evolving chord alternating utonality (dark) and otonality (dark), with short sections for improvising. 
Chris Brown, composer, pianist, and electronic musician, creates music for acoustic instruments with interactive electronics, for computer networks, and for improvising ensembles. Collaboration and improvisation are consistent themes in his work, as well as the invention and performance of new electronic instruments. These range from electro-acoustic instruments (“Gazamba”, 1982), to acoustic instrument transformation systems (“Lava”, 1992), and audience interactive FM radio installations (“Transmissions”, 2004, with Guillermo Galindo). As a performer he has recorded music by Henry Cowell, Luc Ferrari, José Maceda, John Zorn, David Rosenboom, Larry Ochs, Glenn Spearman, and Wadada Leo Smith; as an improvisor he has recorded with Anthony Braxton, Pauline Oliveros, Fred Frith, Rova Saxophone Quartet, Ikue Mori, Alvin Curran, William Winant, Biggi Vinkeloe, Don Robinson, and Frank Gratkowski, among many others. Recent recordings of his music include “ROGUE WAVE” (on Tzadik), “TALKING DRUM” (on Pogus), a duet with Fred Frith titled “CUTTER HEADS” (on Intakt), and “SUSPENSION”, with the CBD Trio, on Rastascan. He is also a member of the pioneering computer network band “The Hub”, which has just released”BOUNDARY LAYER”a box set recording celebrating over 20 years of music on Tzadik. He is also a Professor of Music and Co-Director of the Center for Contemporary Music (CCM) at Mills College in Oakland, California.