Though I don’t often need pure audio tools personally, I thought I’d share a few that have proved to be worthwhile in this thread.
My first entry is a well-known program that provides most of the functions that I need in audio, and is called Audacity. This is an editor and recording program that can be used in Windows, Linux and the Mac operating systems.
Combined with the free ffmpeg and Lame libraries, this tool can open audio directly from video sources, and can output in many different formats, including .wav, .mp3, .ac3, Flac, Ogg Vorbis and others.
Even if you are only a part-time dabbler in audio, this is an essential free tool.