Volume2 is described as 'advanced Windows audio mixer, a complete replacement for the standard Volume Control. Thpplication lets you easily change the sound volume just by rotating the mouse wheel or by using keyboard hot keys or just mouse move on screen border' and is a popular app in the Audio & Music category. There are more than 25 alternatives to Volume2 for a variety of platforms, including Windows, Linux, Mac, Android and Windows S. The best alternative is EarTrumpet, which is both free and Open Source. Other great apps like Volume2 are Background Music (Free, Open Source), Volumouse (Free), QasTools (Free, Open Source) and Sound Lock (Free).
"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.
VolWheel is a little application which lets you control the sound volume easily through a tray icon you can scroll on. It is written in Perl/Gtk2 and works both for ALSA and OSS. You can configure it quickly through its configuration interface.
A floating volume control to help those that have lost the use of their hard volume keys.
It will stay on the screen the whole time but can be closed if watching full screen video, then can be restarted like any normal app.