The previous version (0.3.2) worked for me in Mavericks (macOS 10.9.5); the main "problem" was the humongous icon that stuck down from the screen-top menu bar and couldn't be removed. (Never saw anything that intrusive or hideous before!) But the program itself worked.
It wouldn't launch in High Sierra (macOS 10.13.6) at all, not even enough to "Update" the program… so I went through their uninstall procedure as detailed on the developer's pages on GitHub, then downloaded & reinstalled the newest version (0.4.0), following all the instructions very carefully... and it STILL won't launch at all. Total waste of my time!
I still have the problem that audio in all my web browsers (such as accompanying a YouTube video, etc.) plays much, much softer than the Mac's system volume or iTunes does. Still have no idea why, and with this "Background Music" app non-functional, no idea of a solution. Any ideas? Thank you.