Can I get Apple Music on an iMac 27" Mid 2011 running on High Sierra?

AlfieC,

If you are unable to access Apple Music through iTunes on your Mac running macOS High Sierra, you may be able to access Apple Music using Safari on your Mac. This article has information on how to access Apple Music on the web:

Listen to Apple Music on the web and in apps - Apple Support

Take Care.

Hello AlfieC,

Thank you for using Apple Support Communities!

We understand from your post that you would like to use Apple Music on your Mac. We definitely now how important it is for you to be able to listen to all your music on your Mac as well as your other Apple devices. This article has steps you can use to access your music on all your devices which you may find helpful:

Access your music library on all your devices - Apple Support

Best Regards.

AlfieC,

As stated in the article above, you open the Music app on your Mac to sign into Apple Music. Here is a link to the Apple Music User Guide for Mac which you may find useful:

Apple Music User Guide for Mac - Apple Support

All the best.