Lalo Schifrin was the original choice to do the soundtrack for the film The Exorcist. YouTube claims this was his original theme:

   Director William Friedkin rejected Schifrin’s work turning to Mike Oldfield’s “Tubular Bells” for the theme:

   The history behind this has always claimed Schifrin’s soundtrack scared test audiences too much and the studio asked to have it toned done. Hard to believe after listening to that theme, but when you listen to this recording of Schifrin’s soundtrack the problem of intensity is more obvious.