You can’t completely isolate your app’s audio from the system master volume through normal APIs — the OS mixer always applies the global volume to all playback streams. Libraries like NAudio, CSCore, or OpenAL can control relative app volume, but they still sit under the system mixer, so user volume changes will affect playback.

If you need fully independent control, you’d have to use a custom audio backend (e.g., ASIO on Windows or low-level ALSA/CoreAudio access) that bypasses the system mixer, but that breaks portability and often requires elevated permissions. There’s currently no fully cross-platform way in C# to play audio entirely independent of the system master volume.