Nicotine+
Nicotine+ is a graphical client for the Soulseek peer-to-peer network.
Nicotine+ aims to be a pleasant, free and open source (FOSS) alternative to the official Soulseek client, providing additional functionality while keeping current with the Soulseek protocol.
Soulseek is a file sharing network for mostly Music but also other files. The most available format for songs are MP3, M4A and FLAC. Almost any song/album is on there so you will have no problem finding what you need. You need to share files yourself otherwise there is a possibility you will get banned. I added a YouTube video tutorial so you can understand it better.
Screenshots:
Downloads are available for:
This is by far the best way to get your hands on high-quality, less-mainstream music. Been using it for years now.