iOS: Apple has released a new app, called Music Memos, that tries to make capturing those song ideas you have on the go a little bit easier. In typical Apple fashion, Music Memos is dead simple. When you open the app, you're presented with a big button to record. Tap that (or set it to record automatically), and you can start recording your idea for a song immediately. When you're done, Music Memos will dig into the audio to suss out the chords and tempo. You can then add a simple little bass or drum track to get an idea for how it'd sound. Once you're done getting your idea down, you can also go ahead and add in lyrics, tags or other notes. Essentially, Music Memos is a charged up Voice Memos app with a few handy tricks meant for musicians. You're not going to record a whole album in here, but it will at least help you keep track of ideas.
Music Memos (Free) [iTunes App Store]