Music on Vine - Vine, now with music. Make 6-second music videos.
Abundant Music - Generate royalty free music with a simple but very powerful procedural music creator
Mindie - 10 second music videos (w/ private mindies)
AIVA - The AI composing emotional soundtrack music
Triller - Make celebrity-quality videos with a few taps of your phone
WolframTones - Listen to what I just found in the WolframTones music universe