[CM] Music5

M. Edward (Ed) Borasky znmeb at cesmail.net
Fri May 2 23:49:18 PDT 2008

Bill Schottstaedt wrote:
>> heard it play music via timed loops 
>> and a speaker hooked up to the sign bit of the accumulator register
> This sounds like the computer music I heard when I was about 10 or 11
> years old (1961 or maybe 62) -- on my birthday I got a tour of the
> computer facility where my father worked (a huge room full of IBM's
> or maybe one IBM), and the guys played happy birthday somehow, 
> and were gleefully calling it computer music.  A great present!
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Yep ... actually, there was a "business case" for having that speaker 
tied to a register. One could infer the structure of the computation 
from it, and if by chance one's program had gone into an infinite loop, 
you'd get either silence or a monotone at the frequency of the bit changing.

The Control Data 924 had the top three bits wired as a 3-bit DAC 
(although they were reversed -- bit 23 was the low-order bit, bit 22 the 
middle bit and bit 21 the high-order bit!)

Somewhere buried in a back room I think I have some reel-to-reel tapes I 
made on that CDC 924. There were some timed loops in the operating 
system that had been deliberately coded to make sounds, and I had coded 
some others that took advantage of the DAC structure.

The sounds of computers at work (at least the "slow" ones of that era) 
are fascinating. They're really nothing like the "bloops" and "bleeps" 
you hear in science fiction movies of the time. They have a "fractal" 
structure, there are "buzzes" and arpeggios, and sometimes they are as 
complex as whale songs.

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