Actually, MMR was an all day classical music station. In the beginning, the "underground" only came on after 9 pm!
WDAS was the other one.
But, I think his name was Mike Cutscoona or some such, got busted smoking pot while on air.
We heard a commotion and Mike excused himself and the air went blank.
They were back on in a day or two.
Pierre Robert was in that mix somehow, I don't remember now, that was over 30 years ago and with too much Wild Turkey in between, so don't rely on my memory.
High times in Philly!
Then DAS went black underground and MMR went all day rock.