I have been learning SuperCollider this semester, and just finished up my final project. It is an algorithmic piece and uses some basic additive and subtractive synthesis to make bell and percussive sounds.
The main idea is that some large bells will play notes chosen randomly from a set, and when certain notes are played, other sounds will be triggered and play short segments.
The pitch material is all based on ratios for synth bells that I found in a SuperCollider tutorial: 0.5, 1, 1.19, 1.56, 2, 2.51, 2.66, 3.01, 4.1. In other words, if your bell plays 100Hz, the harmonics will be 50, 100, 119, 156, 200, 251, 266, 301, and 410 Hz.
I made a set of frequencies - a scale if you will - based on these ratios, starting at 100, 200, 400, 800, 1600, and 3200 Hz. The harmonics of each overlap, so when the bells play, their harmonics won't have these exact ratios anymore, but they still sound very bell-like. Each time through the algorithm, the bells will be chosen from a subset of this main scale, so there are slight modulations. Also, since the notes are chosen randomly, they will trigger the other sounds differently each time.
For those interested, I have uploaded the code (in HTML).
I recorded a few versions of the piece. This is the one I liked best:
You can listen to some alternate takes here, here, and here.