Currently the Funklet machine only runs in Chrome (and Webkit nightlies, if that phrase means anything to you). It may soon run in Firefox too.
Holding a number 1-4 and clicking a cell jumps to a particular velocity.
Holding shift and hovering over cells will delete them.
Holding shift & then a number 1-4 and hovering over cells with set them to that velocity.
Hit the space bar to restart the machine.
Hit 'r' over and over again to get more slapback reverb. (Shift+'r' to get less.)
Hit 'v' over and over again to get more volume. (Shift+'v' to get less.)