I try almost any audio creation app for iOS. I definitely have a group of favorites and Polychord is one of them. If you make verse chorus type of music connect Polychord to your DAW and recording. The MIDI generated is a nice secret weapon. Polychord 2 was recently released so if you passed by the original I suggest taking a look at 2.0.
“Shoulda Woulda Coulda, Inc. is readying a major update to their iPad music composition tool, Polychord. The version 2 update brings a vast quantity of new exciting features to this highly-rated app including the ability to record your song data, a new graphical user interface, and Palettes.” – Future Music
For more info: polychordapp.com