Okay, I have to chime in here. Boorman's use of music, especially in his earlier films, is quite remarkable in my estimation and Zardoz is no exception. I was especially struck at the time (and still am) at the use of the 7th Symphony in the main titles. Simply put, the film's arranger (help me here, someone . . . I've forgotten his name) drops out everything but the central melody and its countermelody, which are sung as a duet by by two counter tenors. So intensely did that strike me that I immediately taught it to a girl friend of mine (a friend who was a girl, since I'm a gay male) and we'd sing it together over and over. Ever since then, it's been a fun party game when intelligent and musical friends have gotten together. You'd be surprised how quickly and easily you can teach even moderately musical folks the simpler melody, then sing along with them to the more complicated countermelody.

I've always wanted to get a huge room full of people to do that!

Anyway, the whole film displays a great and very unique use of music like that.