"Bartók Concerto" is a ballet choreographed by Ben Stevenson in 1969, set to Béla Bartók's 1943 composition Concerto for Orchestra.
This video of a partial studio rehearsal of the ballet seems to have been recorded in September of 1972 in Anchorage, Alaska.
The video begins with a shot of a dance studio, where the edge of a dancer's dress is visible on the right side of the frame. After she stands posed for approximately a full minute, she begins dancing across the stage in unison with three other dancers in a row. As the ensemble choreography continues, the camera pulls back and the dancers perform in various "cannon" formations, keeping their hands clasped near their waists--almost religiously. When the music swells, their arms open out and they begin more dramatic choreography (including jumps). Next, the dancers take turns performing solos while the rest remain posed. Each seems to represent a different emotional state, tied to a different musical mood in the concerto. Finally, the dancers all join back together for a brief finale, all ending in a final pose. The video ends there.