Audacity is a audio recording and editing utility. On our business we record a lot of telephone prompts. We always use Audacity to do it.
Audacity allows us to mix in background music and change the volume of the recorded greeting so its optimal for the phone system. It contains a lot of professional features like a compressor to remove the pops and equalize the sound. It makes our jobs easier and our work sound better
The Complete Tutorial to Audacity
Download Audacity from the official site at: http://www.audacityteam.org/download/