Check out this rock cover made with only IOS app.

This is a cover of All Along The Watchtower, recorded entirely with iOS virtual instruments as performed by their respective creators. Vocals were recorded directly into an iPhone (no external hardware). Mixing was done in GarageBand on Macs to simplify collaboration.
There are many excellent examples of iOS-based electronic music, but we feel that rock is under-represented. We banded together to explore getting a great rock sound using nothing but iOS instruments.
Vocals - Adil Sherwani (guitarism)
Lead guitars - ThumbJam through AmpKit via Audiobus
Rhythm guitars (riffs) - iFretless Guitar through Amplitube via Audiobus
Rhythm guitars (arpeggios and chords) - guitarism clean + through AmpKit via Audiobus
Bass guitar - iFretless Bass
Drums - DrumJam