Sources for Free Music

[Emor D'ni Lap]

• The astounding Internet Archive has unfathomable years of listening available, the problem is how to find anything there! You can do a search and you might get what you were looking for: http://archive.org/details/audio - try their "advanced search" feature, too!
  
• The Free Music Archive has an enormous and growing list of contributions, and some useful methods by which they organize their content. Here's their "Music for Video" page, for instance (no, they don't have a "Music for Games" page yet!): http://freemusicarchive.org/curator/video
  
• Incompetech !
  I have no idea what Kevin MacLeod's devious, underhanded scheme is....he must have one, but I have not been able to find it! He's written tons of Very Useful Music, and is giving it away with only the caveat that you credit him when you use it! He seems to have covered almost all bases at his Incompetech site!
  
• Public Domain Music
  MusOpen: a site that collates music in the Public Domain for easy downloading: http://musopen.org/music
  Check out this, for example: http://musopen.org/music/piece/717
  PublicDomain4U, another great Public Domain site with lots to search through: http://publicdomain4u.com/
  And lastly the Open Music Archive: http://www.openmusicarchive.org/
  
  If you have more suggestions, please add them and they'll eventually be collated for a page on the Writers' Guild website.
  

[RaelZero]

I'd also add

• SoundCloud, which has music that is free (gratis), but not always free (copyleft license).
  
• FreeSound, which is more about sound effects rather than music, but there is some.
  

[Calena]

[*]Incompetech !
I have no idea what Kevin MacLeod's devious, underhanded scheme is....he must have one, but I have not been able to find it! He's written tons of Very Useful Music, and is giving it away with only the caveat that you credit him when you use it! He seems to have covered almost all bases at his Incompetech site!

The sites I've used are already listed by Emor and RaelZero, but I wanted to second Kevin MacLeod . He's providing full-orchestral soundtracks with vocals! Outstanding resource for age builders.

[Quetzlcoatl]

Now you can spend even more hours searching for the right sounds, at another amazing source for free music:
https://filmmusic.io/