And then there was early computer music...
When Applied Data Research got its PDP-7 in 1966, there was a DECUS
program to get it to play music by toggling the lower order 4 bits of
the MQ (and the MQ lights) to generate square waves. If you wired that
up to an audio player, you got electronic "music" of a blatting sort, in
four part harmony. (It really needed some analog filtering to flatten
the square waves into curves, but that was beyond me.) Anyway, I spent
much of my free time that summer programming as much of the original
piano score of "Pictures at an Exhibition" as would fit into four parts.
With the buzzing tones, the completely constant volume, and the coarse
controls over note lengths, it sounded utterly bizarre, but... the
computer was playing music! As was said back then, "The marvel is not
that the bear dances well, but that the bear dances at all."
The PDP-7 had DECtapes, and they had their own unique rhythms. DEC's
software was poorly written and could only read a block at a time, so
you'd hear the tape start, reverse, read, stop; rinse and repeat. A
brilliant colleague named Avram Caspy figured out how to insert
optimized routines underneath DEC's software (he used all 8KW extended
memory as a buffer). With his routines, the DECtapes would start,
reverse, and then whoosh at high speed for up to 30 blocks before
stopping. DEC's paper tape routines were equally poor and would
stutter-read; use of interrupts and a short circular buffer made that
continuous and quieter as well.
Another fun set of devices were the very high-speed vacuum pick card
readers that the mainframe companies made. They would blow air through
the card deck to separate the cards and then vacuum pick the top card,
reading and expelling it at breakneck speed (the best readers did 1000
cards per minute or more). Of course, when they broke, you got a totally
different sound, as cards were blown all over the machine room,
typically with the front-edges curled, making them unreadable.
/Bob
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