K509 • Week 2

Introduction to RTcmix

RTcmix is a program that generates or processes sound according to instructions you give it in a simple programming language. Because you use a programming language, it’s easy to make sound in response to an algorithm you design. The algorithm typically incorporates a certain amount of controlled randomness, letting the computer make some of the decisions when rendering the sound.

This is a very different approach from the way we work with sequencer-based tools, such as Digital Performer or Pro Tools, and their collections of plug-ins. Not better — just different. Most people take the sound produced by RTcmix and mix it in a program like Pro Tools.

RTcmix is an open source project that uses the GPL software license. As a result, the source code for the program is free: it doesn’t cost anything, and you have the freedom to change the code. This probably doesn’t sound like a big deal, but it is. It means, at least in theory, that your creative work can be free from the constraints of some company’s business plan. (Ask any former user of Opcode’s Vision sequencer program about this.)

The source code for RTcmix, as well as some documentation, is available at RTcmix.org. You can find compiled packages for Mac OS X (both PPC and Intel) at iub.edu/~emusic/rtcmix/pkg.

Here’s what you should do this week.

  1. Brush up on your Unix command-line skills. (You’ll need them.)

  2. Download and print the RTcmix tutorial PDF file.

  3. The CECM computers have the tutorial example scores; if you’re not on one of these computers, download the example scores.

  4. Read pp. 1-13 of the tutorial, stopping just before “Sound File Input and Output.” Make sure you run the example scores; otherwise you won’t get much out of the tutorials. Be brave, and make changes to the scores. Experimentation is the key to learning this stuff!

  5. Write at least one RTcmix score that uses the WAVETABLE instrument and explores the following concepts or techniques. Be ready to play and discuss your scores in class during week three.
    • looping
    • randomness
    • envelope tables
    • non-sine wavetables
    • pitch computation
    • conditionals
    • arrays


-John Gibson