Goblin & Giorgio Gaslini - Dario Argento Profondo Rosso (Deep Red) 1975 - Official Soundtrack Album

The famous OST of the film, composed and performed by the progressive rock group "I Goblin," formed by Claudio Simonetti, Walter Martino, Massimo Morante, and Fabio Pignatelli, complemented by jazz-rock music from Giorgio Gaslini, was chosen by Argento as a fallback. The director, in fact, had even wanted Pink Floyd to compose it. The band politely declined the invitation, being too busy working on their new album "Wish You Were Here." However, Argento felt that Gaslini's music was not suitable for the film and that something more modern was needed. The first draft of the obsessive little song was deemed simply terrible by Argento, which greatly irritated Gaslini, who subsequently abandoned the project, leaving it unfinished. Initially, the director wanted famous bands at the time, such as Emerson Lake & Palmer or Deep Purple, to perform the jazz musician's music.
At the time, for those who had just seen The Exorcist, the soundtrack of Profondo rosso echoed the piece Tubular Bells by Mike Oldfield, music made extremely famous by William Friedkin's film, which was released in Italy in the same cinematic season, just five months earlier, on October 4, 1974. Recently, Argento has indeed stated that he suggested to the Goblin to draw inspiration from Tubular Bells... (cit. wiki)