KeyboardMixer allows you to change specific application volumes using keyboard volume controls.
By holding Ctrl while using the keyboard volume wheel or button, KeyboardMixer will change only the volume of the currently focused application.
You can also add two custom applications to change the volume of, which will trigger when holding Ctrl+Shift or Ctrl+Alt respectively. To change these, add the name of the application's .exe file into the text field as shown.
While changing an application's volume, a small indicator will appear temporarily, showing the application volume in a manner to the Windows master volume slider. The location of this slider is configurable in the settings.
Download the latest version from the releases page.