In the movie ‘Deliverance’ they first tried “Dueling Tubas” and that guy (who wasn’t Jon Voight but went on to play the evil executive in “Robocop”) played a French horn.
But the tuba player kept passing out.
That would be Ronny Cox.
IIRC, it was Martin Mull who recorded “Theme from Belligerence”, by the Dueling Tubas, after the Deliverance movie came out.
An old vid can be found on youtube. Just him on a tuba, no horn evident.