midi cool

 

We commonly refer to a single MIDI device as a port.  Each MIDI port can
receive (or send) messages on 16 channels.  You can think of each channel
as being a different musician (or group of musicians all playing the same
instrument).

You assign an instrument to a channel using what is called a patch.  All notes
sent on that channel will then play with that instrument.  Much as a musician
may be able to switch instruments within a song, you can change patches within
a song as well.  But typically, no channel can play two different instruments
at one time.

Besides patch changes, you will use note on and note off messages or events.
Each note on event has a pitch and a velocity describing how hard the note is
struck.  You can also add controller events, which manage other functions of
the MIDI device such as, set the volume or other parameters.

In the early days of MIDI, there was no agreement among manufacturers as to
how a device might respond.  Some devices might call a piano patch 1 while
others would play a trumpet.  To alleviate this problem, a specification on
top of MIDI called General MIDI, was defined.  Now most soundcards and
synthesizers will at least support General MIDI as a subset of their
capabilities.  A standard set of patch changes as well as other parameters
were specified.  One item worth noting is that under the General MIDI
specification, channel 10 is specifically reserved for drums while channels
1-9 and 11-16 can be used for melodic instruments.

Further extensions to General MIDI were defined by individual manufacturers,
most notably GS by Roland Corp. and XG by Yamaha.  In the last few years, a
General MIDI 2 specification was agreed upon.  These specifications are all
aimed at making MIDI more portable – in other words, sounding more similar
from one device to another.