Mainframe Music

LaRoy Tymes was teaching himself real-time programming on the CDC mainframe. He created imaginative exercises to explore the big machine’s limits. One of the more imaginative was coaxing the CDC-3600 into playing music: The Tym Before ...

“I just gave myself little exercises. One of them was maybe a bit more ambitious than the others. Control Data 3600s had tape units that had pneumatic tape drives, very high performance. They could read tapes at 200 inches per second and start and stop quickly. I found that if I gave a write command to the tape unit and then aborted the write command before it got past the inter-record gap, I could start and stop the tape as often as maybe 300 times a second, which is in the acoustic range. So you could make a lot of noise with those things.

“So I wrote the Stars and Stripes Forever. I used the console speaker for the piccolo. It had a drum printer, which I used for the percussion. And I had a row of tape units all synchronized so that they were all pulsing together for the trombones.

“And also while I was there, I ported the Stars and Stripes program over to the Control Data 3800 and 3400 with mixed results. The problem on the 3800 was that it had a cache, which made instruction timing difficult to predict. I couldn’t control the timing of my inner loop, so the piccolo on the console speaker didn’t sound too good.

“On the 3400, I immediately burned out the tape controller. And I thought I was in a lot of trouble because those tape controllers cost far more than I could make in a year. I could never pay for it. And Control Data was actually grateful because I pointed out a design flaw that they didn’t realize was there. So rather than get mad at me, they redesigned the tape controller so it could play my program.

“At the beginning of Stars and Stripes Forever when those tape units were going "Baum, Bop, Uppabaum," you could feel it in your chest. Even the building would shake, and for people who have never seen a computer behave that way, it was very impressive.

“It became a standard part of the Control Data maintenance tape. So it got played all over the world. That was my introduction to real-time programming. You might not think of that as real-time programming, but that’s exactly what it was.”

Management wanted to punish LaRoy at first, but his music program was the star attraction on family day. Everybody was just blown away by the thing. He became a hero for it. George Michael, in his Computer History Museum interview, said it was the most impressive demonstration of real-time programming he had ever seen. The Tym Before