Deep Purple for sure was an underrated band that I listen to when I was a teenager. I had their album in 8 track. I liked Blue Oyster Cult's couple of hits also. "Burnin For You", and "The Reaper". Black Sabbeth was another band that I listened to some, that wasn't all that popular. Nazareth was another band that comes to mind, having only a couple hits. Love Hurts, and Hair Of The Dog.