I needed to edit some music and came across Audacity.
Below is a description from PCWorld:
Looking for a good all-purpose audio editor? Audacity is an open-source, free audio editor that lets you record, play, convert, and edit audio files. The program lets you convert files from one format to another, edit sounds easily, mix tracks, and apply effects to your recordings. It also features a built-in amplitude envelope editor, a customizable spectrogram mode, and a frequency analysis window for audio analysis applications. Built-in effects include Bass Boost, Wahwah, and Noise Removal, and it also supports VST plug-in effects.
A 1.3.0b beta version offers improved performance for larger projects and has several new features such as the ability to expand and collapse tracks. However, we recommend using 1.2.4b for maximum stability.
Audacity will work with most flavors of Windows and Linux, Unix and Mac OS X versions are available from the Audacity homepage.
If you want to use VST effects for sound processing, you'll need to install the VST effect enabler by following the instructions here. To save your Audacity recordings as MP3, you'll need to download the LAME MP3 encoder by following the instructions here.
Note: Some anti-spyware packages detect Audacity as containing Buddy Spy 2.2 spyware. This is a known false positive. According to the developer: The compressed Audacity executable happens to have some of the same byte-sequences as Buddy Spy 2.2, but it's just a coincidence. See this page for details.
http://www.pcworld.com/downloads/file_description/0,fid,22513,00.asp