Spotify - Map shows when two people play same song at same time
Volume2 - Volume2 is an advanced Windows audio mixer, a complete replacement for the standard Volume Control.
SoundCloud - Enjoy music & follow favourite artists
Sound Control - App-specific volume control
Last.fm - The world's largest online music service. Listen online, find out more about your favourite artists, and get music recommendations, only at Last.fm
Power mixer - Power Mixer is a complete Windows volume control replacement.