Ccmixter.org have a ton. Also soundcloud. Aside that the usual ways like Youtube.Also keep an eye for remix contests. Plenty of good vocals from a few well know projects/bands for free ,a chance to get featured and earn some $ or other prizes. Source: over 1 year ago

Find some fitting music to use in your videos. Source: almost 2 years ago

Creative commons remix community (some are non-commercial): ccmixter.org/. Source: about 2 years ago

For Free and non-copyrighted samples: CCmixter and Freesound. Lots of good stuff there. Source: about 2 years ago

Http://ccmixter.org/ tons of music with a variety of creative commons licenses. Source: about 3 years ago

Ignore the major labels, there is a vibrant world of new music being released on indie labels! http://avant.fm. - Source: Hacker News / 10 months ago

Tl;dr: crapshoot as to whether you get featured, but worth it if you do. My personal experience with it was positive. I posted my site on PH over the summer (plug: https://avant.fm, a customizable feed of new releases from the best indie music labels). After a couple weeks it was featured for a day. Not sure how that happened, but someone with some pull "hunted" it I guess. About 30 other sites were featured that... - Source: Hacker News / over 2 years ago

Super cool. Would love a "has lyrics" feature (for my player, https://avant.fm). Always wonder how hard that would be. - Source: Hacker News / over 2 years ago

> 3. Discovery is not a viable product I guess define viable? The future has got to hold more ways to interact with music than the main apps of Spotify, Apple Music, etc., which push music in a very specific, generic way. Mostly around top 40, opaque personalizations, algorithms and “algotorial”. We’re never getting back to a place where your identity is defined by which record store you go to. But... - Source: Hacker News / over 2 years ago