If you need beta testers I wouldn't mind testing it before it gets released to the public.
Um, writing isn't my stronger side
so I'm not sure if I can help out much at that part.
As for the song part....hmm...well I don't know about those kinds of songs, but I do know two people who make really nice music while playing the piano. I mean not like personally, but I follow them on sites like YouTube or Soundcloud so I can check out their latest work. So if you're interested I would recommend you to check out their sites/profiles in hope that maybe you can find something you like.