Musical
Instrument Digital Interface:
What is MIDI?
MIDI (Musical Instrument Digital Interface) is a
standardized communications protocol. The objective of the MIDI
standard is to allow electrical instruments and interfaces of different
manufacturers, to control common functions such as note events, timing
events and so forth. MIDI does not transmit audio, it simply transmits
controlling data.
An Example:
Back in the 1970s to early 80s bands would have walls of
keyboard instruments, each instrument having its specific sounds. With
the introduction of the MIDI protocol it was possible to have only one
keyboard, which connects via MIDI cable to a multiple number of
synthesizers regardless of whether or not they were from the same
manufacturer.
How MIDI works
We will start out with a simplified example of a MIDI message, in this
case from a keyboard to a synthesizer:
1. Play the middle C note
with the specified velocity.
2. Apply a vibrato to the note being
played.
3. Stop playing the middle C note.
As the communication protocol is standardized the
synthesizer will understand these commands regardless of vendor.
Midi devices communicate via MIDI cables. All MIDI-compatible devices
have the following jacks: MIDI IN, MID OUT and MIDI THRU. The MIDI IN
port receives incoming MIDI messages. The MIDI OUT port transmits MIDI
messages from one device to another (for example from one keyboard to
another). The MIDI THRU transmits an exact copy of the MIDI message
being received on the MIDI IN port. This makes it possible to create a
chain of several devices and instruments. For the purpose of
controlling several devices MIDI interfaces (pictured below) can come
in handy.
MIDI Controllers
MIDI messages not only have information about notes to be
played, velocity and so forth, they also have standardized controllers
to control “expressive” parameters such as the main
volume, modulation wheel or sustain pedal. The most common controller
is a keyboard, though such controlling commands can come from a
sequencer on a computer. Most modern sound cards have MIDI ports, and
if not can be bought separately at a relatively low cost.
MIDI Controller Numbers
Here is a list of the most common standard controller numbers as
defined on the MIDI protocol:
Number
Controller name
1
modulation wheel
7
main volume
10
pan controller
64
sustain pedal
Recording MIDI
At this point you have to decide what it is you want to
record. As MIDI messages do not contain audio, the recording of MIDI
messages, for example with a sequencer through the MIDI port on your
computer, also contains no audio. However, MIDI recordings a quite easy
to edit. A wrong note can easily be deleted and replaced with a mouse
click. This is something not as easily possible with audio recordings.
Also, the data size of MIDI recordings is very compact, making
transport of songs possible with a single diskette. This is another
advantage of MIDI recordings. If you are not happy with the sounds you
have, you can easily take your recordings elsewhere and play the same
song using alternative synthesizers.