I'm using a computer to assist in the composition of Raw Moon , a set of preludes for Piano. I wrote a bit about the process earlier. I take an image of the lunar surface, a photograph stored online in the NASA archives. Then I use a library of tools in the Open Music software platform published by IRCAM to transpose the pixels of that image into points on a spectrogram. A spectrogram is a visual representation of frequency change over time, so there's a natural correspondence between an image and a spectrogram.
I play back the sound created by that spectrogram, and I upload the sound into another IRCAM tool, one called ASAnotation. This tool lets me set various parameters and thresholds to capture pitch based on the spectrogram analysis. What I'm doing there is reducing the pitch complexity so that I can represent the image in standard western notation, which I can play at the piano.
ASAnotation produces a Sound Data Interchange Format (SDIF) file, which is a markup language that easily translates to MIDI. I import the MIDI file to Sibelius, which produces a score.
I said standard western notation, but the result is very abstract rhythmically, and is filled with dense chord clusters. It's the kind of thing that makes sense to represent graphically, like a Varese score. I've used the material in a couple of different electronic pieces (Moon Ikon) where the capacity of a player is not a constraint. For Raw Moon, I want to extract what I consider musically meaningful artifacts from the original (the raw) material. That's the phase I'm in now, and it probably looks the most like 'composition' in that I have pencil and paper.
I'ved used a computer before, of course, without thinking of computer assisted composer. All of my published scores were created in Sibelius, and all of my extant electronic music was recorded on a laptop or more recently an iPad.
I like to categorize, so let's think about a few different categories of composition that uses a computer.
Computer music is music that requires a computer for the performance. Maybe a sequencer or sampler , some kind of controller that is manging synthesizers.
Computer generated music I think of where the structure of the music is determined by algorithms that have been worked out in a machine. The ready availability of sequencers and software like Iannix make it a lot easier to realize 6 hour pieces structured on your favorite equstion.
Then what I think I'm doing with the piano preludes is Computer assisted. The computer does something that I'm not able to do, because I am a human with limitations of time, skill or sensory perception.
It's like having Merlin or Moriarty as an assistant. Someone capable of transforming objects, or perceiving other worlds clearly, understanding complex mathematics, and with a staunchly virtuosic approach to performance.