It is a cinematic ritual that unconventional film fans have shared in for nearly 40 years, but it has probably never been presented quite so unconventionally.

On Friday night in Damrosch Park, the darkness of a giant cinema screen was pierced by a disembodied set of crimson lips that began to sing an opening incantation to some 2,000 moviegoers. In unison, this crowd chanted along, intoning an a cappella tale of science-fiction monsters and corrupted youth.

Outside observers of this strange sacrament at the Lincoln Center Out of Doors festival would have noticed that something was missing from this showing of “The Rocky Horror Picture Show” — namely, the audio from the movie.

But the seemingly absent soundtrack could be heard by the audience members who wore wireless headsets that glowed green, blue and red, in what Lincoln Center described as a “silent” screening of “Rocky Horror.”