The octave buttons are used to shift the keyboard up or down in one octave increments. This extends the range of the keyboard in either direction, which lets you play notes that lie outside the number of keys available.
The button is used to select independent banks of continuous controllers. Effectively, this allows you to control more independent parameters with the knobs, faders and buttons. The bank selector button is used to switch among the available banks.
The more buttons the device has, the more complex the input can be.
Faders can be either channel volume faders, pitch sliders, crossfaders or even EQs.
A sustain button works in the same manner as a traditional sustain pedal. Pressing the sustain button and playing a note causes it to sustain. However, the sound will not stop until the button is pressed again.
More knobs (rotating controls) can give the user more dedicated control over the device – e.g., volume, effects, EQs, etc. Types of knobs may differ between endless type or step type.