Dir2ogg
- Python script that converts MP3, WAV, and M4A files to Ogg format.
- http://badcomputer.org/unix/dir2ogg/

GramoFile
- Assists in moving gramophone records onto CDs. Filters out hiss and pops.
- http://www.opensourcepartners.nl/~costar/gramofile/

Cdgtools
- Suite of tools for handling CD+G karaoke disks and files.
- http://www.kibosh.org/cdgtools/

Gnome Wave Cleaner
- An audio cleanup tool for GNOME. Handles WAV, MP3, and Ogg.
- http://gwc.sourceforge.net/

MusE
- MIDI/Audio sequencer with recording and editing capabilities.
- http://www.muse-sequencer.org/

PyKaraoke
- CDG/MP3+G karaoke player. Can search inside Zip files.
- http://www.kibosh.org/pykaraoke/

Grip
- Cd-player and cd-ripper. It also provides an automated frontend for MP3 and other audio format encoders.
- http://nostatic.org/grip/

Rosegarden
- MIDI sequencer and notation editor for Unix-like systems.
- http://www.rosegardenmusic.com/

Zero Tolerance's Cue Creator
- A small Perl script that allows you to create CUE and MP3/OGG/WAV-files from audio CD's.
- http://www.x-a.be/index.php?page=14

TiMidity++
- MIDI player, converter to wav. Uses Gravis compatible patches and can play these through soundcards lacking their own patches.
- http://sourceforge.net/projects/timidity/

The TAON Project
- A sound editor for Linux.
- http://www.informatik.uni-frankfurt.de/~eschenb/taon/

Linux Sampler Project
- Audio sampler with features similar to hardware samplers. Offers speed, high audio quality rates, supports common sample library formats.
- http://www.linuxsampler.org

Lilypond
- Creates beautiful music notation from text input. Outputs Postscript, SVG or MIDI files. GNU license.
- http://lilypond.org/web/

CoverViewer XMMS Plugin
- Displays covers or images related to songs. Internet cover retrieval facility. Handles tagged files, CDs, and streams.
- http://coverviewer.sourceforge.net

IMMS: Intelligent Multimedia Management System
- Playlist plug-in for XMMS that tracks the user's listening patterns and dynamically adapts to suit tastes.
- http://www.luminal.org/phpwiki/index.php/IMMS

Philip's Music Writer
- A music typesetter. Input is a plain text file, output is in PostScript.
- http://www.quercite.com/pmw.html

BEAST/BSE
- GTK+/GNOME based front-end to BSE framework to simulate audio synthesis and tracking composition.
- http://beast.gtk.org

Baudline Signal Analyzer
- Realtime signal analysis and spectrum analyzer tool.
- http://www.baudline.com

ZynAddSubFX
- Synthesizer with two engines, realtime polyphonic, Midi support, microtonal capability, effects.
- http://zynaddsubfx.sourceforge.net

Orpheus
- Text and window mode audio player for CDs and MP3 with CDDB interface.
- http://konst.org.ua/orpheus

Mixxx
- Open source DJ mixer.
- http://mixxx.sourceforge.net

Sound Processing Kit
- An object-oriented class library for audio signal processing.
- http://www.music.helsinki.fi/research/spkit

Geoff and Dave's Audio Mixer
- A digital audio mixing package.
- http://gdam.ffem.org/

XMMS-SID SIDplay Plugin
- Plug-in for playing Commodore 64 music (SID tunes) with XMMS. Requires libSIDPlay library (link given).
- http://www.tnsp.org/xmms-sid.php

GNOMAD
- GTK+ client program for the NOMAD Jukebox, using libnjb and id3lib to handle communications and ID3 tagging.
- http://www.df.lth.se/~triad/krad/gnomad/

AlsaPlayer
- PCM player written for ALSA driver and library, supports other outputs like OSS and esd. Plug-in interface.
- http://www.alsaplayer.org/

GLAME
- Free and extensible Linux/Unix audio editor. GNU licence.
- http://glame.sourceforge.net/en/index.var

xmp: Extended Module Player
- Open source (GNU GPL) portable module player for Unix or Win32.
- http://xmp.sourceforge.net/

SoundTracker
- MOD tracker for X, similar to FastTracker. Includes a sample recorder and editor.
- http://www.soundtracker.org/

Aumix
- Adjusts an audio mixer. X and ncurses interfaces.
- http://jpj.net/~trevor/aumix.html

Audio File Library
- An API for accessing a variety of audio file formats.
- http://www.68k.org/~michael/audiofile/

Matti Koskinen Software
- Programs including a de-noiser, MIDI generation from fractals, sound creation from gifs.
- http://www.sci.fi/~mjkoskin/

Ecasound
- Audio software for Unix.
- http://www.eca.cx/