A little over a year ago, I reviewed the Capo app, which is a music learning tool made by SuperMegaUltraGroovy. The developer, Chris Liscio, has released Capo 2.0 today. In addition to providing the ability to slow down and loop music, Capo now provides the ability to automatically detect chords within songs. Also included in the new version is a sophisticated Spectrogram that helps you visualize the music being played. This Spectrogram can also be used to help tab out songs as you play through them.
These updates make an already excellent music learning tool even better. If you have a Mac and play guitar, I highly recommend checking the Capo app out.