Audacity is a cross-platform multitrack audio editor. It allows you to record sounds directly or to import Ogg, WAV, AIFF, AU, IRCAM, or MP3 files. It features a few simple effects, all of the editing features you should need, and unlimited undo. The audio I/O uses PortAudio, which fully supports OSS, Mac OS X CoreAudio, and Windows WMME, and can be compiled with support for ALSA and Jack.
Find Duplicate Music Files detects music files that contain the same music, even if the files are differently named, and are in different formats such as MP3, OGG, WAV, WMA, M4A, and RealAudio and contain different or non-existent meta-information such as ID3 tags. The program operates on whole directories of music files, analyzes them, and outputs the filenames of pairs that seem similar, based on their audio fingerprint or perceptual hash.
The Snack sound extension adds commands for sound play/record and sound visualization, e.g. waveforms and spectrograms. It supports in- memory sound objects, file based audio, streaming audio, WAV, AU, AIFF, and MP3 file formats, synchronous and asynchronous playback. The visualization canvas item types update in real-time and can output postscript. New commands and file formats can be added using the Snack C-API.
Synaesthesia is an eyecandy program that represents music graphically in real time as coruscating fields of fog and glowing lines. It is intended as a visual accompaniment to music. Its display combines information about the frequency, location and diffuseness of sound. It can take input from CD, line, piped from another program, or from EsounD. It also functions as a CD player.
The MusicBrainz client library (also known as mb_client or libmusicbrainz) is a library for developers that wish to add MusicBrainz metadata lookup capabilities to their applications. It calculates CD Index IDs and Relatable's acoustic fingerprints, and looks up the metadata associated with the calculated IDs.
MP3val is a tool for validating and optionally fixing MPEG audio files. It was primarily designed for MPEG 1 Layer III (MP3) files, but also supports MPEG-1, 2, and 2.5 Layers I, II, and III. It can be useful for finding corrupted files, such as those that have been downloaded. It supports ID3v1 tags (which must be at the very end of the file), ID3v2 tags (at the very beginning of the file), and APEv2 tags.