Apple Music will not open just crashes.

Hello, sanderbrinks.

Thank you for contributing to Apple Support Communities. We understand that you’re experiencing an issue where the Apple Music app isn’t opening on your iMac, and you’ve already done some extensive troubleshooting to try and resolve it. 

Let’s try these steps, testing the Music app after each.

• Update the macOS on your iMac, if applicable. Issues like this are sometimes addressed in the small macOS updates that Apple releases.

Update macOS on Mac - Apple Support

• Check to see if it’s possible the issue is with your current library. Make sure the Music app is not open, and hold down the Option key as you click to open it. You should see a window that asks you to either create a new library or choose a different library.

Use multiple libraries in Music on Mac - Apple Support

Still not able to keep the app open? 

• Create a new user on your Mac and log in there to test. If it stays open here, but not in your main user, you know the issue is user specific. 

Set up users, guests, and groups on Mac - Apple Support

• Finally, if it happens in the new users we know the app itself is the issue, and the only way to reinstall the app is by reinstalling the macOS software on your iMac. This is a good time to create a Time Machine backup if you manage your iMac with backups. Then, start up from macOS Recovery and reinstall the macOS. This step may take awhile, but your data should remain intact. 

How to reinstall macOS - Apple Support

Cheers.