From Audacity Wiki
Audacity uses a number of libraries:
- LibNyquist - A language based on LISP with support for functions on sounds.
- PortAudio - Cross-platform Audio I/O library.
- PortMixer - Cross-platform Audio Mixer library (sound level controls, input source selection)
- LibMad - MP3 uncompression.
- LibId3Tag - Tags for MP3
- LibFlac - Lossless compression and uncompression
- LibOgg and LibVorbis - Fully open source compression lib, similar to MP3 but free from patents.
- SoundTouch - effects to change the pitch or tempo
- LibResample - high-quality sample rate conversion
- wxWidgets - Cross-platform GUI development library and general cross-platform development tools.
There are also plans to make the structure of Audacity more modular by 'factoring out' library material. These plans often end up on the back burner.
- LibAudacity - A sound file manipulation library with no GUI functionality.
- LibApp - GUI components that could be fed back to wxWindows team as enhancements, for example the code in Audacity which handles key and mouse bindings, docking toolbars, buttons that change state when you hover over them are general GUI elements that would be useful to other application builders.