Akai MPC Reference Manual page 119

The length of a sequence can be set from 1 to 999 bars, which would be enough to create an
entire song using only one sequence. However, the MPC software has a dedicated SONG mode
that lets you chain sequences together to create a song.
Song
The MPC software has a special song mode that allows you to arrange different sections (verse,
chorus, hook, etc.) in order to build a song. Each song can have up to 250 parts and the MPC
software can hold 20 songs in its memory.
Sustain
The term "Sustain" describes the level of an envelope remaining constant after it has passed the
Attack and Decay phases. Once reached, the Sustain level is kept until the trigger is terminated.
Track
A sequence offers 64 tracks and each track can record notes and controller data. For example,
you can record the verses of a song on Track 1, while recording the choruses on Track 2.
Alternatively, you can record different instruments on each track.
Note that your performances are recorded as MIDI events and the actual digital audio is not
recorded onto a track. That way, you can edit your performance in many different ways once the
performance has been captured.
Trigger
A trigger is a signal that initiates events. Trigger signals are very diverse. For instance, a MIDI
note or an audio signal can be used as a trigger. The events a trigger can initiate are also very
diverse. A common application for a trigger is its use to start an envelope.
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