Conference napalm::commusic_v1

27.0. "MIDI Software For PDP Engines" by GRDIAN::RIES () Tue Jul 24 1984 16:14

I have been interested in computer music and synthesizers for a long
time but do not know how to play any instrument myself. Most of the
folks who use this notes file seem to be way out of my league when
it comes to musical talent and knowledge. However, musical knowledge
or not I have been working on a Music compiler and player software
on and off for several years now. It is all based on the PDP10
music compiler which I believe originally came from MIT. I got the
PDP10 sources a few years back and the sources to about 150 songs.
I then built a cheap tone generator board using some TI chips and
wrote a player program for the PDP11 that would play the songs
compiled by the PDP10 compiler. (I have a PDP11/23 system of my
own at home). This got to be a pain so I set out to write a version
of the compiler for the PDP11. I got the initial version of this
running a couple of months ago. With this you can now compile and
play songs all on the PDP11. About two months ago, a friend introduced
me to the world of MIDI. This is what I had been waiting for. I
bought a Roland Juno-106 since it seemed to have the most functionality
as far as MIDI was concerned. The next problem was how to interface
MIDI to a standard RS-232 serial line since MIDI is 5ma current loop
at 31.25 Kb. A friend of mine had a PDT-11 which does not have the
capability of an external baud rate so he built a small micro-based
interface that does the proper conversions and allows connection
to any serial line run from 1200-9600 baud. It buffers data from the 
high baud rate MIDI side. This is not ideal for real time stuff, but
for non-professional use its fine. On the other hand my system can
except an external baud rate so I built an interface the converts
the 5ma to EIA and supplies a clock at 500HZ to a standard serial
interface. Therefore I can run mine at the full MIDI baud rate. Both
of these interfaces are Bi-directional. The interface I have is fairly
simple to build and cost is minimal. I have since upgraded my player
software to "speak" MIDI. So given the compiler and the player you
can now play your synth the easy way. I have also written a patch
librarian which lets you read patch information from the 106 and store
it on the computer for later loading. You can have as many libraries
as you want and patches are stored and loaded with the name of your
choice. This will interface with the compiler and player to allow
you to specifiy patches within a song and have the player load them
in real time. Also, I have plans for making the player be able to
play multiple synths (multiple voices) and do real time MIDI channel
selection to find a synth that has a free voice for playing songs
written for multiple instruments. One other piece of software that I
have is a MIDI utility program which lets you monitor a MIDI device
and display all MIDI messages in mneumonic format. This lets you find
out what types of messages your instrument is capable of sending.
You can also send data out the MIDI for experimental purposes.

   There are currently 4 of us with these interfaces, Juno-106 and
software and we have many ideas of what we would like to be able to
do with it all in the future. All the software is still in a development
phase but it is functional. If any one is interested in any of the
hardware or software details, contact me or respond to this note.
As it stands now, all the software runs on a PDP11 under RT11. I
will soon be modifing it to run on RSX and P/OS on the PRO.
The format of the data output from the compiler is fairly simple
and a player could be written for any random computer. I would like
to encourage anyone who may be interested in doing this and giving
them help. I realize that there are not many people with their own
PDP11's.

		GRDIAN::RIES	Frank Ries