This input FX is used to capture computer keyboard presses and transform them into note events, so you can play synths without a MIDI controller. The up and down arrow keys will step between octaves, and the following keys will play notes:
black keys: 23 567
white keys: qwertyu
black keys: sd ghj
white keys: zxcvbnm
Note that the note keys extend a little beyond the specified range, so that the bottom octave overlaps with the first, to make playing easier.