Writing in the New York Times, Dave Kehr called Bruce Posner’s 19-hour box set Unseen Cinema: Early American Avant-Garde Film 1894-1941 “one of the major monuments of the DVD medium.” Yet one peculiarity of this medium is that its monuments are easily overlooked, and this 174-minute program, part of a touring series that also stops at the University of Chicago Film Studies Center later this month, offers a rare chance to sample Posner’s uncommon discoveries on the big screen, most in their original formats. The box set defines avant-garde broadly enough to include Busby Berkeley production numbers and home movies, though some of the latter come from seminal experimental filmmakers Rudy Burckhardt, Lewis Jacobs, and Joseph Cornell (whose efforts from the 1930s have recently been brought to presentable completion by Lawrence Jordan). This program is anchored in the mid-30s and provides splendidly offbeat evocations of that era, but it also includes sound tests from the mid-20s that were sold to Fox’s Movietone, and most of the silent films have been furnished with excellent musical scores. Thu 10/20, 8 PM, Northwestern Univ. Block Museum of Art.