The interesting thing is I discovered that the PB really did multitask - I used the VoiceNotes app to record my sterling piano playing a week or so ago. But obviously the internal recording will be more fluid.
It's very difficult to play. It'd be better if black keys were only activated by a press in the upper half of the screen, and the white keys only by the bottom half of the screen, because the keys are too thin to play precisely.
i think keys are fine, the recording option is a great addition, very well done.
Suggestion, LOOPING, quantized looping would make this an outstanding app.