Testing Gestrument a music synth, what can I tell the makers?

Hi folks,
I just purchased Gestrument LE.
This is a music making app which allows the user to perform within a prepared set of sounds and musical parameters by swiping your finger across and up and down the screen.

The biggest issue that I've found is that when voiceover is on, the sounds do not play when simply touching the playing surface. If I doubletap, then they work, but that sortof negates things.
When I set things up, and then turn off VO, then I can play the instrument.

What does this mean, and what can I tell the authors so they can make things better?
Also, I'm not sure whether the sliders work properly with VO. How can I know, and what should I tell the devs.

Thanks!
Rusty