Dr Phibes, the inverted ventriloquist?

A ventriloquists dummy adopts life through a voice given to it. Dr Phibes cinematic appearance is the morbid inversion of this. The watcher knows that the voice is supposed to come from Dr Phibes, and indeed, knows that it does - but is given no animate correlate to the voice. The voice is half way between the standard talkie formulation (a voice coming from a seen source) and acousmatic (a sound with an unknown source). Dr Phibes grim mask (masking any vitalism) cleaves a horror between the two poles of cinematic vocalic formal norms.

The Acousmatic/Ventriloquised Voice of Mercedes McCambridge in The Exorcist

Mercedes McCambridge - listen from 05:55.

then.

The Exorcist Scene Dissected:

Watch from 1:56 first then go back to the first scene - better that way!