From: utzoo!decvax!cca!hplabs!hao!menlo70!sytek!zehntel!teklabs!tekcrd!azure!laurir@sri-unix
Newsgroups: net.followup
Title: Re: More Computer Music
Article-I.D.: azure.1468
Posted: Thu Nov 11 18:49:05 1982
Received: Tue Nov 16 04:59:21 1982

I'm surprised that nobody's yet mentioned the old PDP-10 music system.
The device was originally known as a KL10, for "music KLudge", and
connected to a KA10 processor.  Later "KL10" was officially used to name
the third generation PDP-10 processor.
  The box watched the low order six bits in the data register lights
(via direct connections) to produce six individual square wave voices.
You could mix each voice into any combination of the two stereo output
channels by twisting potentiometers.  A standard stereo "auxiliary input"
would take it from there.  As usual, there was a music compiler.  Alas,
the music player had to run stand-alone, so it was only heard when major
pieces of hardware were broken (like a 16k core box).
  One of the features of the KA10 processor was a speed control knob
next to the power switch.  Presumably the service engineers would
adjust it to make the processor clock fire at an optimal rate.  While
music was playing, this knob could be used to slow it down, much like
reducing the speed of a turntable.
  -- Andrew Klossner (decvax!teklabs!tekmdp!laurir)