Computer Music and GACSS

In addition to my works of cut/paste computer music, instrumental compositions, and works for low trumpet, I have also composed a number of pieces for computer music alone or computer music with a solo or ensemble.

For a full listing of my musical works, including a link to download them all as MP3s, visit my compositions page.


When I started working with computer music around 1990, the technology was quite different than what we have available today. Computers didn’t come with sound cards, there was no SuperCollider or Max/MSP, and disk space to store created sounds was extremely limited. To engage with the medium, I got my start working in the UIUC Computer Music Project, a lab which provided a home-built digital-to-audio converter (DAC), and a Music-V type language to work with called Music 4C. I authored (coded) various instruments for Music 4C and used them to create new works, including “Uninduced Approximation.”

By 1992 a sound card was “affordable” for a typical PC, and I wrote a grant to fund development of a new original software package called GACSS (Genetic Algorithms in Composition and Sound Synthesis). This grant was funded by the UIUC Campus Research Board, and thus began a many year path of creation and collaboration. My collaborator on the grant was Zack Browning, one of my composition teachers at the time. Zack Browning used GACSS in the creation of new works for many years, and produced a CD called Banjaxed. The works on this disc are all for instrument and computer-generated sounds, and the sounds are almost entirely created using GACSS. I highly recommend you get a copy of this disc and check it out.

GACSS (Genetic Algorithms in Composition and Sound Synthesis)

GACSS is a software package I wrote that allows the composer to graphically visualize sound at the period level and turn this visualization into sound events (waveforms) with variance over time. Periods are designed in terms of length (pitch), curvature, and complexity. A number of breakpoints are specified, and the types of curves between those breakpoints can be set (e.g. linear, exponential, or inverse exponential). To create an event using that period, GACSS then repeats the created period until the duration has been achieved. However, that period is not copied verbatim, but is instead modified on each repetition based on the ‘trans’ value.

the transPeriod() function from GACSS

The trans value defines the window in which temporal transformations of the waveform at the period level can drift from the waveform’s center. One can think of this as a degree of noisyness. The higher the trans, the more the nosie. The principal relies on the fact that as long as a number of successive periods are similar enough, they will be percieved as belonging to a single pitch, even if they change over the course of that event. The more distorted the period becomes from the original, the more the sounds becomes noise.

Genetic Algorithms (GAs) were chosen as a method for timbral search. The number of parameters available to the composer can produce an infinite number of possibile sounds. A GA was added to help the composer find timbres of interest within this ‘search space’ of possible sounds.

Why GACSS Isn’t a MIDI Synthesizer

GACSS can be used to generate both pretty and ugly sounds. But one thing it doesn’t do is produce sounds that mimic traditional instruments. This is by design. Others use technology to recreate those things we already have. I want to use technology to create new sounds and visuals that we can’t create otherwise. I like to find what the machine is good at and exploit that instead of trying to get it do what I’m already good at.

lotted ebb

mix whit

Over the years of 1992-1998 I composed a number of works using GACSS, both for sounds alone (we called it ‘tape’ back then), and for instruments with sound. lotted ebb and mix whit are solo tape pieces and were composed specifically for premieres at the 3:2 New Music Festival in New York City. You can read more about these works on my cut/paste computer music page.

If But Or

If But Or is another tape piece and was composed for the 3:2 New Music Festival in Wesleyan Connecticut, and was my first work created using GACSS. If But Or was issued on a CD titled waveFORMation, Electronic Music Studios CD EMS 9700, 1997.

Not Pitch

Saxophonist Rhonda Taylor performing Not Pitch at New Mexico State University, 2009photograph by: Robert Yee

Not Pitch was written for North Carolina School of the Arts Professor and saxophonist Taimur Sullivan. The work, for baritone saxophone and computer-generated sounds was premiered by Taimur at the Settlement Music School in Philadelphia, PA. In recent years, New Mexico State Professor of Saxophone Rhonda Taylor has toured the work around the United States as part of her 2009-2010 concert season. On March 2, 2012, Rhonda released a new recording of the work on her CD titled Interstice.  This is available on iTunes, Amazon, and CD Baby.

Epistatic Niche

Epistatic Niche uses ideas from natural genetics and the workings of genetic algorithms as a compositional model. The work is for trumpet, piano, percussion, and computer-generated sounds. It was written for the UIUC Contemporary Chamber Players’ 1994 Southeastern United States tour. It’s most recent performance was in 2004 at a Faculty Composer’s Concert at the Krannert Center for the Performing Arts.