MUSIC

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► Desktop Apps

Youtube-dl - Command-line program to download video/audio from Youtube videos and other sites.
Youtube-dl-GUI - Desktop GUI for youtube-dl for those not proficient in using the command line.
FreezerPC - Streaming and downloading app for Deezer. Builds available for Windows and Linux
Deemix - Desktop app for downloading mp3/FLAC from Deezer. Replacement for Deezloader.
Chimera - Supports downloading music from multiple platforms.
Soulseek - Desktop app that connects you to a P2P network used for downloading music (any format). Unlike bittorrent, the protocol used here is direct P2P i.e. downloading and uploading is not done with multiple users simultaneously but with a single user (like downloading a file from a website). This provides more security than public trackers as there is no swarm for copyright trolls to stay in and monitor. Though there is no quality control here, the chances of encountering low quality files is still quite low. For people wanting to share their libraries, soulseek is the easiest and fastest way.

Spotify and Deezer modded apps to allow full ad-less streaming available at Mobilism.
Freezer - Streaming and downloading app for Deezer.
AIDS - Android app for downloading mp3/FLAC from Deezer. Replacement for deezloader
Fildo - Android app for downloading and streaming music.
Newpipe - Watch and download youtube videos. Also offers ability to download from soundcloud.
Youtube Vanced - Ad-free youtube, supports background play. Modded version of the official youtube app.
YMusic - Youtube Music player and downloader

/r/MusicalBootlegs - Broadway bootlegs
Jimmyr mp3 search - Custom search and downloader to find mp3 files on google.
leakedalbums.org - New music albums
pluspremieres.to - iTunes releases (m4a)
free-mp3-download.net - High quality music downloads (mp3/FLAC). Uses only unintrusive banner ads.
mp3juices.cc - Searches for audio on several sources, such as youtube and soundcloud. Allows downloading in mp3 and streaming.
khinsider.com - Mp3 streams & downloads. Video game scores/soundtracks.
squid-board.ru - Video game, anime, and TV & Cinema scores/soundtracks.

rutracker.org [.org, .net, .nl] - Russian tracker with an extensive music catalog (any format).
nyaa.si - Anime OSTs
music-torrent.net - Music torrents

[Semi-Private] en.metal-tracker.com - A very nice tracker for metal music.
jpopsuki.eu - Aka JPS. Music tracker for various types of music such as Japenese, Korean, Chinese, Thai, etc
animebytes.tv - Aka AB. Anime OSTs
Redacted.ch - Aka RED. FLAC, mp3, m4a. Best music private tracker. One of the harder trackers to maintain ratio on.
Orpheus.network - Aka OPS. FLAC, mp3, m4a. Second best music private tracker, after RED. Much easier ratio economy compared to RED. In addition, there is a thread where you can request any torrent available on RED, without putting a request. This provides full access to RED without the hard economy. It is highly beneficial to have accounts on both trackers.