The first single of the band, "Slunečný hrob" (transl. "Sunlit grave"), was a huge hit in 1969, but their existence as a mainstream act was a short term thing. After a couple of years they were forced to change their style into a mostly instrumental form of jazz-rock, for two good reasons.
First, the Soviets went extremely harsh with the censorship, forbidding politically conscious lyrics and basically every word about freedom. Second, the oppressors enstabilished a professional musician license, which was refused to every rock band who didn't compromise with the governement requests. The only chance to make professional music without being labelled as "one of them", was the instrumental way (that explain why jazz-rock and instrumental progressive rock was widespread there at the time).
I have hereby uploaded the first single and the first EP of the band, with Vladimír Mišík on vocals. He left them in 1970, to join Flamengo, while guitar player Radim Hladík went on, releasing experimental albums throughout the Seventies.
"Slunečný hrob" is a wonderful, tragic ballad, reminding me of Scott Walker, David Bowie, and Procol Harum. "Sen není věčný" is a pop gem that mixes baroque pop, samba influences, and science fiction elements. The remaining tracks, sung in English, are not as brilliant.