# Technical Information

Capo can play songs in MP3, M4A, AIFF, and WAV formats.

iTunes Store purchases can be played in Capo, provided the song is in iTunes Plus format. Protected songs are not supported in Capo.

Note: As of January 2009, the majority of music in the iTunes Store is no longer protected by restrictive DRM, and you can convert many of the songs you already own to iTunes Plus format. See the iTunes Store for details.

## Changing playback speed without affecting pitch

This is not new technology, or magic. This time stretching technique has existed for years, and modern computers are fast enough to apply this complex operation in real-time (and leave some extra cycles behind for nicely-drawn waveforms!).

In addition, Capo takes advantage of the built-in time stretching functionality that ships with Mac OS X, and is used in many other professional audio software packages that ship on the Mac.

The technique is described in some detail here at Wikipedia:

http://en.wikipedia.org/wiki/Audiotimescale-pitchmodification