InD

An Exploration of Semi-Aleatoric Sound

Music 220A

Daniel Hollingshead and Brian Lewis

Fall 2009

http://ccrma.stanford.edu/~theseus/220a/InD.wav

Note: The file is large, so it'll probably play best if you save it to your desktop and play it from there. Cheers!

Terry Riley's In C is one of the most famous pieces of minimalist music composed in the 20^th century. The piece consists of 53 different phrases of varying lengths, anywhere from under a measure to around ten seconds long. The performers play the patterns in sequence, but there's a catch: Each performer determines how long she wants to play a particular pattern. The entire ensemble slowly moves from phrase to phrase, with the fastest performers two or three phrases ahead of the slowest. One player plays repeated eighth notes which serve as the piece's metronome--The Pulse, as Riley calls it. Because so much is left up to the individual performers--even the instrumentation and number of performers are not standardized--the piece is considered semi-aleatoric: no two performances sound the same. Our project's inspiration comes from this piece and its creative impact is felt throughout.

To begin, we adapted a piece of ChucK code from Jim Bumgardner designed to play interlocking phrases to create our own take on semi-aleatoric music. The code instantiates an array of StK instruments, each of which runs through phrases written as MIDI notes with associated volumes and durations. The minimum and maximum number of phrases played by each performer can be set according to the ChucK-ist's wishes, as well as the piece's tempo and instrumentation. As the repetitions each performer plays of a given phrase are determined using bounded randomness, the code preserves the irreproducible aspect of In C.

Next, we used this code-skeleton to compose a semi-aleatoric piece in ChucK a la In C. Rather than work in the key of C major, however, we used D Dorian, a key whose accidentals are the same as those of C major, but which is built on the D minor triad (D, F, A). One of In C's distinctive characteristics is its slow harmonic movement. At points in the piece, listeners are led to feel that the desired resolution is imminent, and yet Riley deliberately keeps us in suspense. In response, we wanted to create a piece that is driven by intense downward movement--the sunset to Riley's sunrise, in a sense. Due to our mutual love of video-games, we included several references to Koji Kondo, the Legend of Zelda composer known for his works in the Dorian mode.

We then felt like the piece needed another voice, something more acoustic to make the song feel more alive. But including such a human element was risky with a piece whose force derived largely from its randomness. We wanted something which would accentuate the uniqueness of each performance without ruining the concept. With this limitation in mind, we decided to simply improvise different trumpet lines to different iterations of the code. Iannis Xenakis, another famous 20^th century composer, composed some game-theoretic pieces (such as Duel and Strategie) in which two composers controlled their own orchestras according to their whims to play one of several options in response to the choices of the other. The performer in this case attempted a kind of man-versus-robot version of such pieces, having certain lines in mind before recording, but allowing the choices of the opponent to dictate the flow and dynamics.

With the trumpet recording and ChucK composition in hand, we then melded the two together in Audacity, putting some light effects on the trumpet, mostly just a light reverb to compensate for the recording quality. We also made some creative decisions as to editing out certain parts of the trumpet line when the chaos seemed overwhelming.

After that, we thought the piece merely needed some mood and setting, so we turned once more to ChucK. Since our programming ability is (sadly) limited, we found two templates for some weather noises by Kijjaz on a ChucK forum, then spent quite a bit of time adapting these templates to create the multiple different kinds of wind sound heard throughout the piece as well as the rain heard at the end. An interesting note is that the wind and rain are again semi-aleatoric, i.e. they evolve randomly. Thus we hope the original spirit of the piece remains uncompromised.

We hope you enjoy!

--Daniel and Brian

Delineation of Roles (although each of us helped the other a good deal):

Brian composed the main ChucK line.

Daniel composed and performed the trumpet line, composed the wind and rain in ChucK, and edited the piece together in Audacity.