How to get Modulation in Music Studio iOS App?

I really like Music Studio and use it a lot on my iPad, mostly playing the sounds via a wind synth Midi controller. However I have one problem which doesn’t occur in other apps: when I activate Modulation on my controller, nothing happens in Music Studio ; the note stays straight and flat.

I find pitch bend works perfectly from my controller, so am puzzled why modulation doesn’t. When I use other synth apps (eg. Korg iM1, Thor, Garageband etc), modulation works fine.

Surely modulation must be available in Music Studio? If so, please can someone explain how to activate it. Thanks!