Cannot delete composer data from Apple Music

I use a third-party music player on my iPhone (Cs Music, FWIW). It works perfectly with Apple Music, however...

About 75% of my collection is classical, so I naturally use the composer field to sort tracks. However when I sort by composer, the list gets clogged with songwriter credits for non-classical works. Even though I delete the composer field on the desktop app, it always reappears in the iOS app.

Presumably the iOS Music app is syncing its data with Apple's own library and is then filling in the gaps. This then gets transferred to Cs Music, messing up my composer sort list. And no, I can't edit the files in Cs.

It's irritating rather than disabling, but is there any way to clear the composer 'junk' that I'm experiencing?

(When I say junk, this is no disrespect to the songwriters of course. It's just info I don't need.)