Just to round this ramble out - I was right Primephonic was the app I was thinking about - sold to Apple Music who shut it down. I’m doing a free trial with IDAGIO anyway.
Is it any good?
It’s OK - sound quality as good as QoBuz, and search seems to be better designed for Classical than QoBuz. It’s lacking in album info which I quite like but at 9.99 it’s not too badly priced. It’s probably not that much better than QoBuz that it’d make me subscribe.