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From: ron@BRL-TGR.ARPA
Newsgroups: net.music
Subject: Re:  The popular MIDI music/computer interface
Message-ID: <6505@brl-tgr.ARPA>
Date: Sat, 8-Dec-84 20:24:43 EST
Article-I.D.: brl-tgr.6505
Posted: Sat Dec  8 20:24:43 1984
Date-Received: Mon, 10-Dec-84 03:11:37 EST
Sender: news@brl-tgr.ARPA
Organization: Ballistic Research Lab
Lines: 50

Turns out the MIDI interface users group (or whatever) went bust.  Some
aquaintance of mine claims to have the spec, but I haven't been able to
worm it out of him.  From looking at the schematics and information
provided with the Roland IBM-PC interface, we came up with the following
conclusions:

	Each midi plug is a uni-directional twisted pair line running
	at 36 Kb (or maybe it was only 19.2).

	The data is serial eight bit bytes.  One bit is a tag to indicate
	whether this is the first byte of multibyte messages or not.
	They list the "unit independent" codes in the Roland manual.

	Each synth typicallly has three MIDI plugs, in, out, and thru.
	In receives commands and interprets them.  Thru is just an out-
	going copy of in for chaining.  Out contains commands from the
	keyboard and controls of this synthesizer.  There are 16 channels
	which are just "addresses" so you can talk to the synthesizers
	individually.

	Most computer interfaces usually have an option to echo there in
	signals on the out plug so that you can put them in the loop between
	your favorite keyboard and the rest of they synths.  The keyboard
	only instruments like the Roland MDK also echo the in on the out
	since they really don't do anything with the in signals.

As far as interfaces go, I know of three.  They are the ROLAND, the Garfield,
and the Passport.  The passport is the cheapest (around $150) and the
hardware is not intelligent.  All the work is done bythe host software.  I've
seen this one on the apple.  It works adequately, but they intend to come out
with better editing programs.  I've not seen the Garfield in use so I can't
comment.

The Roland (which costs about $500, once you get everything) has a little
external processor box.  This box, when in smart mode, records the incoming
notes, timestamps them, and buffers them going into the machine.  It's a
little more eloquent.  You can bypass the buffering if you want.  It comes
with a little eight track recording program and two prerecorded songs.  The
program is fairly nice, but hitting reset seems to send crud out on the midi
and this sometimes zaps my DX-7.  The two songs provided (LISZT which seems
to be Liebestraum and BJ (a jazz piece, possibly Bob James?) are really neat
demos.

I'd personally go with the Roland, except I may end up with the passport
or in addition.  The DX-PRO software which is an intelligent screen oriented
set up of DX-7 voices and includes 800 additional voices, only runs on the
passport and an apple.  I hear the guy who wrote it, quit before doing any
IBM versions.

-Ron