Curious regarding the iPad, what version of iOS is it running?
The dial changes the note progression by altering the pseudo-random seed. The slider brings in different drum patterns and bass depending upon its position.
Light is similar to a "D-Beam" ( which is an IR distance sensing input you get on Roland synthesizers ) although not quite as effective- if the light level changes substantially, it will play a note corresponding to the new light level. When things are getting a little more rounded off, I'll tinker around and see if I can make it more generally playable.