From LQWiki

Audio Conversion Software

The following are some very useful programs for audio conversion. SoX has a horrible interface but can convert many formats to many others and can apply filters, rate conversions, etc. These are scriptable and very useful when processing large groups of audio files.

• SoX Sound Exchange is the Swiss Army knife of sound editors. It can convert from just about any file to any other.

• LAME MP3 Encoder able to encode from wave and other formats into MP3.

• MPG321 which may be used to decode from MP3 to wave.

• LIBMAD MP3 decoder software.

• sneetchalizer a CLI script which converts between several different formats and preserves meta-tags.

Also See

• Audio conversion

  Examples of audio conversion scripts