Audio acquisition

All commercially available digital audio players can play music that has been ripped from Compact Discs via computer. In addition to ripped CD tracks, many digital audio players can accept downloaded music from online music stores. However, such stores often use proprietary formats and DRM, which means that the tracks can only be played on suitably licensed and restricted devices. For example, purchased songs from iTunes might not work on any DAP other than an Apple iPod.
There are also music online communities such as GarageBand.com where music is available at no cost under Creative Commons licenses.
Another way of getting audio files is to rip the songs from radio broadcasts. Many players have the ability to record songs played on the built-in FM tuner. Recently, a Swedish company called PopCatcher has developed a technology to save songs from Internet radio and can distinguish between songs, DJ talks, and commercials for convenience.
Reference : http://en.wikipedia.org/wiki/Digital_audio_player