From: bull@vaxc.cc.monash.edu.au
Newsgroups: alt.guitar
Subject: Re: What is MIDI?
Date: 8 Jan 93 12:18:11 +1100
Organization: Computer Centre, Monash University, Australia

ikeda@ohara.info.waseda.ac.jp (Satoshi Ikeda) writes:
> Hello. Please don't mind my poor English.
>
> ponte@aer.com. (Rui Ponte) writes:
>
>  >explain what MIDI stands for? I have seen it in many posts and
>
> MIDI stands for Music Instrumental Degital Interface.
> And, it decides the standard.
> For example, the transport rate of degital signals is 38400 bit / second,
> you must send the binary code 90H 3cH 40H to instruments to make C sound.
>
> You can harmonize an instrument and another one or computers that have
> this interface, though they are made by different makers.
> So MIDI is used many ways, like synthesizer, drum machine,
> music sequencer, MIDI guitar ,etc.
> To use MIDI guitar, you can make a shynthesiser sound, record the sound,
> and edit the sound. It's great.

        Just to clear a point or two; MIDI is based on a set of standard
messages. These messages tell an electronic musical device to do things
like play a particular note, change the volume by a certain amount,
perform a pitch bend, change to a different sound, etc. When you play a
MIDI device (eg a keyboard or synth guitar) the processor in the MIDI
device makes a message for each note you play. You can record these
messages and replay them. A lot of people like to explain the recording
and replaying by using a tape recorder as an example. This is not a
good example because a tape recorder records sound. A recording of MIDI
messages is not based on any particular sound, it is simply a set of
messages which the processor in a MIDI device understands and uses.

        A much better example of recording and replaying MIDI messages
is this document you are reading. If I recorded this message by speaking
into a microphone and then sent you the tape, you would hear my voice
saying the words you are reading. By typing this message onto a computer,
you get the words I want to say, but without any idea of what my voice
sounds like. Recording MIDI messages is the same. You record the MIDI
equivelent of the words I have used to write this document, without
recording the actual sound you used when you played the music.

        How do you record MIDI messages, and what can you do with them?
As I said, when you play a MIDI instrument, it's built in processor
creates a message for each note, volume change, pitchbend, etc. You can
buy a specialised device called a MIDI Sequencer, which when plugged
into the instrument you are playing, can record these messages. Some
MIDI instruments come with a built in Sequencer (eg. the Korg M1 keyboard
and Roland GR-1 guitar synth). You can save these messages to a floppy
disk (if the sequencer has a floppy disk drive) and replay them any time
you like. You can also change the messages. If you played a couple of
wrong notes, you can find the messages for those notes and change them
to the notes you meant to play. If the timing was sloppy you can fix it,
if you want to change the key, you can, of you want to change the pitch
to another octave, you can, if you want to change the tempo, you can.

        Many people use a personal computer as a sequencer. To do this
you will need, a personal computer ;), a MIDI interface which will let
you connect a MIDI instrument to the computer, and a Sequencer program
to let to record, edit, save and replay the midi messages. The range
of interfaces and Sequencer programs is quite large. There are interfaces
and programs for PC's, Apple Mac's, Commodore Amiga's and Atari ST's
(Atari computers come with the interface built in, for the others you
have to buy the interface seperately). The advantage of using a computer
as a Sequencer is the larger display screen (specialist sequencer devices
only have little LCD displays), more RAM to record the MIDI messages into
(letting you record longer peices of music), and if you have a mouse (and
if the Sequencer program can use the mouse), running the program and using
it's features such as editing can be easier than using the limited controls
(buttons, knobs, sliders, etc) a specialist Sequencer device has built in.
Some Sequencer programs will also let you print the MIDI messages you have
recorded as standard musical notation.

        MIDI is a standard used by all the companies who make electronic
musical devices. I have a Korg Keyboard, a Roland guitar synth and an
Amiga computer. I can make a recording of the MIDI messages of some music
I have written and give that recording to someone else with equipment
made by other companies, and they will be able to use my recording. They
may not be able to use exactly the same sounds I used when I recorded it,
but the sound will be the only difference. The pitch, timing, tempo, etc,
will all be the same. To replay a recording of MIDI messages, you simply
get your computer or Sequencer unit to send those messages back to a MIDI
instrument and the processor in the instrument will read the messages and
perform them as instructions.


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