User guide

Tracktion 4 Reference Manual
9
Introduction 3: MIDI Basics
If you are unfamiliar with MIDI, then perhaps the best analogy to start working with is one of those old
player pianos — the kind with a large roll of punched paper that allowed the piano to play itself. MIDI is
a modern version of that punched roll; it tells an instrument what notes to play, and a little about how to
play them. In fact it is from these devices that the term “piano roll” used to describe MIDI editors in se-
quencers is derived.
A common misconception is to see MIDI data as being the sound. It is important to realise that MIDI
is little more than a list of instructions that an instrument can follow. Much like a sheet of musical score,
MIDI data by itself is rather abstract.
In practical terms, MIDI data is made up of three types of MIDI events: note events, controller events,
and program changes. In reality these groups are not quite so clear cut, and there are other types, such
as system exclusive (sysex) messages. For the purposes of working with MIDI in Tracktion though, the
three groups above are all you really need to be aware of.
Note Events
A MIDI note event tells an instrument to play or stop playing a given note. When a key is struck on a
keyboard, a MIDI note-on event is generated. The note-on event tells any attached MIDI devices which
note was played, and the velocity with which it was struck. The MIDI note is considered to be held until
a note-off event is generated by releasing the key. Velocity typically corresponds to “loudness,” but it
may also affect the timbre of a sound; consider the way a piano sounds when keys are struck hard.
Controller Events
Most synthesizer keyboards have pitch bend and modulation wheels that allow the keyboardist to
add extra character to a performance. These controls generate controller events that typically are used
to change some nature of a sound over time. The modulation wheel for example may add a vibrato
effect to a synthesizer performance. Most controllers are known as “continuous controllers” as they
maintain their current state without needing to be held. In the same way that the modulation wheel will
physically stay where you leave it, so too will the control changes generated by the wheel.
Technically pitch-bend is not a continuous controller, but for the purposes of working with Tracktion, it
can be regarded as one.
Program Changes
A program (commonly referred to as a patch) in MIDI terms is one of the different preset sounds
available on a MIDI device. A typical synthesizer may be able to emulate pianos, organs, violins, and
bass sounds. Each of these different sounds would be a program. A special set of controller events can
be used to change the current program on a MIDI device, but Tracktion makes it even easier by offering
tools and options to insert program changes into edits.
MIDI Channels
Many MIDI devices are capable of playing more than one instrument at a time. Such devices are
referred to as being “multi-timbral.” A multi-timbral MIDI device may be able to play a piano part, a
percussive part, a bass part, and a ute, all at the same time. In order for the device to know which
instruments are expected to play a given note received from Tracktion, the instruments are assigned a
MIDI channel.
You can think of a MIDI channel as being broadly like a radio channel. In the same way that an FM
tuner may be tuned to a radio station, the instruments in the MIDI device will only respond to MIDI
events that are transmitted on their channel.