I don't know what u are considering underground but I like Windy City.
Possessed a dracula musical has some great songs (thrown in with some cheesy ones) but its definitely a pretty cool rockish musical adaptation.
I love the score to Windy City. I assume it flopped because of the book, but I'm quite surprised there was never a Broadway mounting of the show.
If you really want a gem, try and find a copy of the Saucy Jack and the Space Vixens London cast CD. They are extremely rare and loads of fun. The show is a British cult hit similar to that of Rocky Horror. People would actually come to the show dressed as the characters. It's about a trio of hot space chicks who fight the evils of the universe with the power of disco. And to coincide with another thread, there are lesbian characters, one of whom sings the song "Ride My Bike". The Space Vixens are trying to solve a string of intergalactic murders committed by the Slingback Killer who stabs his victims with 4-inch spike heel shoes.
The author is a friend of mine and I saw a wonderful production of the show at the Edinburgh Fringe Festival in 1999. For pure camp fun with a score you can dance to, I highly recommend it. Check out the website.
Saucy Jack and the Space Vixens
I agree with everything that has been said so far... but the first thing that came to my mind was Little By Little.
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