Akai iMPC - Manual (Page 8)

The Variation Slider affects the same four Parameters that 16 levels does,
but on a smoothly sliding scale. This lets you create subtle variations while
recording. Touch the Slider to alter the selected Parameter on the Data
screen.
Experiment with using the variation slider in conjunction with 16 Levels and
Note Repeat!
Erase
The Erase button lets you easily remove notes from a Track. Hold down
Erase and Tap or Hold pads during playback to erase notes. You can also
erase the entire track: hold down the Erase button, and press “Erase Track”
on the Data Screen.
Undo
After recording, the Undo button will light up; tapping it discards the last
recorded take.
TRANSPORT CONTROLS
<< >>
Tap to rewind or fast-forward by one bar.
< >
Tap to rewind or fast-forward by one beat.
Tap Tempo
Sets the tempo based on the speed at which you tap the button. Tap Twice!
Record
Press and hold this button, and the Play or Play Start button to start
recording. While Recording, any previously recorded notes on the current
Track will be erased (imagine a tape recorder).