Music on Vine - Vine, now with music. Make 6-second music videos.
Sound Control - App-specific volume control
Mindie - 10 second music videos (w/ private mindies)
Volume2 - Volume2 is an advanced Windows audio mixer, a complete replacement for the standard Volume Control.
Triller - Make celebrity-quality videos with a few taps of your phone
EarTrumpet - Volume Control for Windows