Release Sonar tells you when the artists in your music collection put out something new. No account, no sign-up: everything stays in your browser.
Pick your music folder, paste a tree or find listing, or just type a few artists. Only folder and file names are read, never your files.
You confirm the doubtful ones. Each artist has a page with the whole discography: mark what you have, what you want and what you want to ignore.
You will see what came out since your last visit and what is coming soon. With Google Drive, the same library is on all your devices.