Apps with 'Per-app volumen control' feature

EarTrumpet is a powerful volume control app for Windows.

"Background Music can pause your music player app when other audio starts playing and unpause it afterwards. The idea is that when I'm listening to music and pause it to watch a video or something I always forget to unpause it afterwards.

Spatial Sound Card replaces the USB box that comes with 5.1 surround headphones, so that you can have surround sound on regular headphones for free. Also includes a volume booster and psycho-acoustic bass boost.

Sound Control adds per-app volume and EQ controls to your Mac apps. Route your apps to different audio devices. Add volume controls to your devices.

Mute notifications, lower your music, & change the volume of games while staying immersed. Overall system volume, notification volume, and volume of individual apps can be adjusted from the menubar.

Displays information and current volume level for all active sound components on your system, enables saving a sound profile into a shortcut file to load later, or changing individual settings via a shortcut file with extensive command line support.

Power Mixer is a complete Windows volume control replacement. It includes audio mixer, scheduler, hot keys support, command line support, the ability to store and recall different presets.