I-pad + geo-synth as midi controller:

https://www.youtube.com/watch?v=E3wfqKSLS...DF989EEB554F058

listen to the sax, which is typically a difficult instrument to emulate with most midi controllers. The ability of a glass surface to allow a wide range of percussive, sliding, strummed or plucked note-on triggers makes it particularly well-suited for use as a MIDI controller for many instruments.

Yeah, most synths have a pitch wheel.. .but there is something more intuitive about sliding up to the note in the same way you would with a fretless instrument.