Back in the day, every major label had a ‘progressive’ subsidiary which would put out all the music thought to be a bit radical and odd. What we might call good. I’m sure you all know what the labels are; everything from Harvest to Deram. And you can be guided by them. It’s not a guarantee, but it will push you in the right direction.
However, for every Ten Years After there was a Clyde McPhatter. Not that there’s anything wrong with him, but if you’re looking for Deram to deliver a Moody Blues-style band into your ears, you will be disappointed.
All labels did this. For example, Harvest put out music by Marshall Hain who was not in the least progressive. I always felt it was a silly thing to do. You might think you’re going to hear something progressive on then end up with a Mungo Jerry record. I especially hated them.
But to confuse you further, Yes, an uber prog rock group were on Atlantic not on Elektra which Atlantic bought and was a more hip label, but Pink Floyd were on Harvest and Genesis on Charisma, which was not originally a mainstream label and really only became one on the back of Genesis success.
So you can use what label a record is on as a guide to what the music is like, but don’t be surprised if you end up with a Prelude album and not some spacey guitar record.