If you're serious about your music, there's a new app for that. Songcatcher is a mini studio app that lets you record ideas for tunes - by humming into the phone.
It doesn't just record in audio though - thanks to MIDI support, you can save the tune as one of several musical instruments: Piano, Electric Piano, Drums, Bass, Guitar, Distorted Guitar, Synth, Organ, Strings and Horns.
You can also tap out the tune in your head on a a resizeable virtual keyboard and layer up to ten different recordings in a single song (or 'project'). Plus, add a tempo to help with arranagement, and mix different songs and email them to yourself.
It's more a musical notepad than a veritable song creator (Ocarina, anyone?) but if you're a musician bubbling over with song ideas, check out the app at Apple's App Store, where it's already clocked up 40,000 downloads in two weeks.