The Polish Singer, Czeslaw Niemen.
He was probably the greatest musician/singer nobody outside of Poland has ever heard of.
Bema Pamieci Zalobny Rapsod - A Mournful Rhapsody In Memory of Jozef Bem
http://www.youtube.com/watch?v=OAeOMVJ4ijc&feature=related
Then there is Janos Kobor of Omega, from Hungary
IT all seems a bit over the top now, but these guys were really pushing the limits in soviet territory at the time