Apple has released GarageBand for the iPhone and iPod touch [iTunes link], bringing the popular music creation tool from the iPad to the company's smaller iOS devices. Offering a range of keyboards, guitars, drums and basses, each supporting Smart Instrument custom chords so that those with less musical talent than they have ambition can still get involved, GarageBand also allows you to plug in external instruments and run them through the app's amps and stompbox effects.
Alternatively, you can use the microphone on your iPhone/iPod touch to record vocals or other ambient noises. Up to eight tracks can be recorded, mixed and released as an audio file, all from your iPhone, plus there's a sampler, 9 amps and 10 stompboxes. Apple packs the app with 250 professional samples to get you started, and exports are in standard AAC format or can be sent as GarageBand files to the desktop app.
GarageBand for iPhone and iPod touch is available now [iTunes link] for $4.99. If you've already bought the app for your iPad, you can re-download it to your smaller iOS device for free, by heading into the "Purchased" section of the App Store.