Computer Keyboard is an Interaction block. It allows you to create playable synths by letting you trigger any connected Source blocks using your computer keyboard, with a key layout that emulates a piano keyboard. Pressing a key will set the pitch and trigger a note/sample in Source blocks, using either monophonic or polyphonic voices.
It’s options let you switch the ‘Voices’ between monophonic or polyphonic. ‘Octave’ sets a transpose up or down across all connected Source blocks, and ‘Glide’ sets the time it takes for the pitch to transition, or glissando between notes, when in monophonic mode. ‘Octave’ can also be set directly on the keyboard using the Up & Down arrow keys, or the NumPad + and - keys.