Amarok is a free music player for Linux and other Unix-like operating systems. Multiple backends are supported (xine, helix and NMM).
Clementine is a cross-platform, open-source, Qt based audio player, written in C++. It can play Internet radio streams; managing some media devices, playlists; supports visualizations, Audioscrobbler API. It was made as a spin-off of Amarok 1.4 and is a rougher version of said program.
Exaile is a free software audio player for Unix-like operating systems that aims to be functionally similar to KDE’s Amarok. Unlike Amarok, Exaile is a Python program and uses the GTK toolkit.
Muine is an audio player for the GNOME desktop environment. Muine is written in C# using Mono and Gtk#. The default backend is GStreamer framework but Muine can also use xine libraries.
Quod Libet is a GTK based audio player, written in Python, using GStreamer or Xine as back ends. Its distinguishing features are a rigorous approach to tagging (making it especially popular with classical music fans) and a flexible approach to music library management. It supports regular expression and Boolean algebra-based searches, and is stated to perform efficiently with music libraries of tens of thousands of tracks.
Songbird is a cross-platform, open-source media player and web browser. It is built using code from the Firefox web browser. The graphical user interface (GUI) is very similar to Apple iTunes, and it can sync with Apple iPods. Like Firefox, Songbird is extensible via downloadable add-ons. It's able to display lyrics retrieved from the net, and also the ones embedded through metadata (ID3v2 tag) after adding the LyricMaster plug-in. Linux official support for Songbird was discontinued in April, 2010. But in December, 2011 a group of programmers forked it openly as Nightingale.
Music Player Daemon based
Cantata is a Qt-based front-end for Music Player Daemon.
Audacious is a free media player for Linux or Linux-based systems. It can be expanded via plug-ins, including support for all popular codecs. On most systems a useful set of plug-ins is installed by default, supporting MP3, Ogg Vorbis and FLAC files. Audacious' classic interface looks and feels very similar to Winamp. It is compatible with LADSPA plug-ins.
DeaDBeeF (as in 0xDEADBEEF) is a modular audio player for Linux, *BSD, OpenSolaris, macOS, and other UNIX-like systems.
JuK is a free software audio player for KDE, the default player since KDE 3.2. JuK supports collections of MP3, Ogg Vorbis, and FLAC audio files.
mpg123 is a real time MPEG 1.0/2.0/2.5 audio player/decoder for layers 1, 2 and 3 (MPEG 1.0 layer 3 a.k.a. MP3 most commonly tested). Among others working with Linux, Mac OS X, FreeBSD, SunOS4.1.3, Solaris 2.5, HPUX 9.x, SGI Irix and Cygwin or plain Windows. It is free software licensed under LGPL 2.1.
Sound eXchange (SoX) is a cross-platform command-line audio editor.
X MultiMedia System (XMMS) is a GTK1-based multimedia player which works on many platforms, but has some features which only work under Linux. XMMS can play media files such as .ogg, MP3, MOD's, WAV and others with the use of input plug-ins. It is a free software audio player similar to Winamp that runs on many Unix-like operating systems. However, development of XMMS has been deprecated in favor of XMMS2, a new audio player built from scratch on the more modern GTK2 libraries. See also Audacious on this page as a successor to the historic XMMS.
Tomahawk is a cross-platform music player built with social media and multi-source music streaming in mind. It features support for services like Spotify, Grooveshark, Dilandau, SoundCloud, 4shared, Jamendo, Last.fm, Ampache, Owncloud, Ex.fm and Subsonic.
Distributions and add-ons
dyne:bolic, a Debian-based live cd/dvd distribution for multimedia production.
Musix GNU+Linux, a discontinued live cd/dvd distribution based on Debian.
Planet CCRMA, an add-on for Red Hat Linux with many tools and system mods.
puredyne, a discontinued Ubuntu-based distribution.
Ubuntu Studio, an Ubuntu-based distribution geared toward multimedia.
AVLinux, a Debian-based distribution intended for multimedia content creation.