I do not recall hearing it before - I like it.
I loved Mountain's first album, but lost touch with them after that.
My favorites are completely obvious - "Mississippi Queen" and "Theme for an Imaginary Western."
In "Theme," I think the blend of Pappalardi's voice against the guitar is truly beautiful.
According to Wiki, Pappalardi produced Jack Bruce's original recording of the song.
In the late 1970s, I drove up to a rock and roll club north of Ft. Lauderdale - in Boca Raton or Deerfield Beach - and saw Leslie West playing with a band I had never heard of before.
West was hugely overweight and intoxicated. At the time I assumed he was broke and about to join the pantheon of Rock Legends who died young.
Congratulations, Leslie West, for making it to age 75!