The occasional collaboration project between two Slovak influential rock musicians, singer (and rhythm guitarist) Pavol Hammel (leader of the band Prúdy) and keyboardist Marián Varga (founder and leader of the highly acclaimed progressive rock band Collegium Musicum) had its roots in late sixties, when Marián Varga, had become a member of Prúdy for around two years. As a duo, they released four albums:
- Zelená pošta (Green Mail) - 1972
- Na druhom programe sna (The 2nd dream channel) - 1976
- Všetko je inak (Everything is different) - 1989
- Labutie piesne (Swan songs) - 1993

Radim Hladík, Czech guitarist and a founding member of Blue Effect made a guest appearance on the first album and was listed as a full fledged third artist in addition to the usual duo on the second album. He did not, however, appear on the subsequent albums.

The two also collaborated on other projects and they often made appearances on each other's bands' albums. Read more on Last.fm. User-contributed text is available under the Creative Commons By-SA License; additional terms may apply.