Alessandro Alessandroni – Cielo Verde {1970s}

Can be found on Alessandro Alessandroni And Nora Orlandi ‎– Music For Strange Situations.

Wikipedia says:

“Being an accomplished whistler, Alessandroni collaborated with his childhood friend Ennio Morricone on a number of soundtracks for Spaghetti westerns. Morricone’s orchestration often calls for an unusual combination of instruments and voices. Alessandroni’s twangy guitar riff is central to the main theme for The Good, the Bad and the Ugly. Alessandroni can be heard as the whistler on the soundtracks for Sergio Leone’s films A Fistful of Dollars, For a Few Dollars More, Once Upon a Time in the West, Pervirella, and many others. Alessandroni founded I Cantori Moderni, an eight singers choir, in 1961. They provided vocals for numerous soundtracks, including those by Ennio Morricone and Piero Umiliani.”