On May 31, 1972, a show burst onto the stage of the Lyceum Theater rehearsed to within an inch of its life. It had to be — and not just because its director was a notorious perfectionist. The re was only one chance to pull it off.

Directed and choreographed by Bob Fosse for Liza Minnelli, “Liza With a ‘Z,’ ” the film of that concert, was a profound meeting of artist and muse. In “Liza,” humor, not smut, defines sexy, and the elfin Ms. Minnelli, 26 at the time, delivers that with perfection . It’s not just that she knows what she’s doing, but that she couldn’t be any other way.

The concert was broadcast on NBC, but shown only three times; eventually, it was restored and remastered. In 2006, “Liza” was presented on Showtime, and ever since, this nearly lost piece of art has been available for the watching — even on YouTube. It remains a spellbinding example of the art of performance, where endurance and skill braid with courage and grace. Ms. Minnelli doesn’t merely sing and dance: She turns herself inside out.