Mac: Want to record tracks from iTunes Radio? AirPlay Recorder exists for those moments and can record any song played over iTunes Radio.
AirPlay Recorder works exactly the same as any live recording software. Hit record and it will start recording in real time, much like you used to have to do when you recorded songs from the radio onto a cassette. AirPlay Recorder does this by registering itself as an AirPlay device that you send the audio to through iTunes. It's a pretty simple idea, but if you want to check it out, the free version of the app lets you play around with it by recording 10 second samples.