Apple used to have a "Music Memos" app for recording musical memos. It also identified chords and allowed you to add auto-generated bass and/or drums. Sadly it was removed a year or two back and users were told to use garage band instead.
For iPhone and Mac, there's Capo which will identify chords and gives a pretty spectrograph for identifying individual notes and tabbing it out.
http://supermegaultragroovy.com/products/capo/
Another option (windows, mac, linux) is Transcribe!