Oh, my, chiptune-eyed surprise
Gambi is an interesting app that allows you to remix and play around with chiptunes. It includes a free track that you can mess about with, though the actual app itself is $7, if you want to take the plunge. The layout is quite attractive, and the Game Boy-styled narrative at the beginning caught my attention almost immediately.
Build playlists, remix and sample your favorite tunes, and check out the bundled tracks included from bands like Blitz Lunar and Hally. If you've got an ear for remixes (Grimecraft?) it might be worth your time to check out.
iOS chiptune remix app [Tiny Cartridge]