/ music via AM-radio (~750 kc/s)   (26.6.92)
/ rhythm with teletype ASR 33
/
/ copyright (1992)
/ National Centre for
/ Minimal- and Retro- Computing
/ Stuttgart - Germany
/
/ Klemens Krause (loops)
/ Mark Tell Schneider (music)
/
/
/
Here are the music pieces we arranged for PDP8-e and ASR 33

Beatles: When I'm 64, 
J.S.Bach: Menuett,
Radetzky March
and a german folk song: kein schoener Land in dieser Welt


When we started making music, we had no example of such a program, we only
knew that such programs exist.
So we started experimenting, what in a pdp-8 would produce optimal RF-
radiation. We found out, that it's not the frontpanel, or the lamp drivers
from there. You can lock the switch register and blank the panel and that
makes no difference in the radio receiver. 
Finally we don't know what exactly we are receiving. We only know, that in the
region of 750 kc there is a reasonable signal near the upper left corner of
the front panel.


The program consists of two loops in the core memory, one at the low end
at adrs 0200 and one at the high end at adrs 7600. The audio frequencies
are generated by switching between these two loops for the time of the
length of the desired period duration.
The trick is, to do this with four voices simultaneous, and also to have a
Teletype ASR 33 with a real tin-bell and audible impact of the printing
drum for rhythm generation.

So I think the program makes no sense on emulators and DECmates and other
6100-stuff. I didn't check, if the duration-ratio between the machine
instructions of a 6120-CPU is the same as for a PDP-8e .
Perhaps it is possible to rewrite it for a DECmate, but that is certainly not
simple. And eventually modern computer (as DECmates) are better shielded than
real computers (as PDP-8s) so that the radiation is too low, to hear it in a
radio.



Klemens Krause
krause@azu.uni-stuttgart.de
