Slavko Vorkapich was an auteur who spoke to Lucas as a fledgling film student. One piece, in particular, was his short Forest Murmurs, which paired hypnotic shots of the wilderness with Richard Wagner's composition of the same name.
Moods of the Sea is yet another of Vorkapich's pieces that impressed Lucas and influenced his early work. He spent much of his student career making projects he called "tone poems" which are reminiscent of this non-narrative short film.
It is easy to see how another of Vorkapich's works, The Life and Death of 9413: A Hollywood Extra, influenced the work of Lucas. The work with miniature models is both expressive and remarkable.
Arthur Lipsett's 21-87 is a bizarre, engrossing montage film. Its influence on Lucas is so well-known that J.J. Abrams referenced it in Star Wars: The Force Awakens with Finn (John Boyega)'s ID number: FN-2187.
Jean-Claude Labrecque's 60 Cycles, a documentary short on the so-called Tour of New France (Canada) is simply mesmerizing. The movie, which features from Booker T. and the MG's, inspired Lucas to make an avant-garde documentary short of his own while he was at the University of Southern California.