This has had a big price drop from $19.99 to $1.99. If you don’t know the app here’s the description.
As seen in Guitar World Magazine’s list of 50 Best Guitar Apps. Capo helps you learn to play the music in your iPod library. By slowing down the music without affecting its pitch, you can learn to play it slowly, and then speed it up as you improve.
You can drop markers at key points in the song, and set loop points to repeat them. In addition to letting you choose songs from your iPod library(*), Capo will let you quickly add the currently-playing song from your iPod, placing the cursor right where you left off listening. For more information, and to watch some videos of Capo in action, check out the Capo website at http://capoapp.com. (*) Capo supports WAV, AIFF, MP3, and Unprotected AAC formats. iTunes Plus purchases are supported, but older iTunes purchases are not. Most music can be upgraded to iTunes Plus—please see the iTunes store for more details.
There’s also a Mac version that retails at $49.99