Wow I really like this app, this is the kind of stuff people have been dreaming of for a long time now so, thanks!
I do have just a couple of suggestions though;
1) There should be an "Auto Delete Notes" feature that can be turned on or off for each layer - this way the user could change the melody in every box instead of having to hit the notes over again in every loop cycle in order to remove them from the sequence.
2) Its great that you've designed a pitch control ("Tone") but what about volume (or velocity) for each layer... I mean common it's obvious.
3) Why can't I save a session?
4) is there a chance you'd add a feature that enables the user to select how many boxes to play (rather then just having one), then i could just flick through them (kind of like in the "Korg Electribe" app, if you're familiar with it).
5) since this app is free and you're selling the extra features... I think that if you add all the above as a bundle that includes all synths and drums and the Wave export feature then you've got a winner because this is a really intuitive musical tool (I'd even call it a musical instrument)
Thanks,
Amir
