"Four American Composers Part II: Philip Glass and Robert Ashley" is a superb music program that will play at the Gene Siskel Center on Tuesday January 4 at 6 p.m. and Thursday January 6 at 8 p.m.

The program consists of a pair of intellectually challenging documentaries about two cultural giants in the world of avant-garde music and experimental performance. The two films were commissioned by the BBC, and originally aired on British public television along with films about the unconventional vocalist/composer/dancer/choreographer, Meredith Monk, and the brilliant composer/poet/philosopher/mushroom expert John Cage.

The documentaries were directed by Peter Greenaway. He was an excellent choice for the project because he shares much in common with the four artists. Like them, he is also a multimedia artist interested in redefining traditional artistic genres and breaking down the boundaries between them. He has a sculpting background and many of his films such as "The Pillow Book" and "Drowning by Numbers" collapse different art forms together

Philip Glass started out as a minimalist, but his work has gradually become more complex throughout the years. He has done countless film soundtracks including "Koyaanisqatsi" and "The Thin Blue Line." I once saw him perform his wonderful score for Jean Cocteau’s "Beauty and the Beast" film live with a small group while the film was showing. The new score was actually worthy of the film classic. In addition, Glass did the riveting, modern opera "Einstein at the Beach." To some listeners Glass’s pieces seem redundant but to his fans they are purposefully repetitive and hypnotic.

The Glass documentary combines classic Glass performances (including many numbers from "Glassworks") and informative interviews with both Glass and his distinguished collaborators.

Robert Ashley is not as well known as Glass, but his work may be just as innovative and important. The Ashley documentary includes "Perfect Lives (Private Rules)," a seven episode opera made specifically for TV (it uses the strengths of the medium to its advantage). The episodes are interspersed with revealing dialog explaining the bizarre and almost otherworldly performance.

Ashley often recites his words in a dry, monotone voice while a series of screens in the frame present images connected to the dialog.

We also see some of the words Ashley recites written in letters on the screen. The use of words and numbers images thematically linked to on-screen images and dialog is reminiscent of Greenaway’s own work, especially "Drowning by Numbers."

‘The Four Composers" is mandatory viewing for anyone with a passing interest in experimental performance or avant-garde classical music. It’s nearly as idiosyncratic and fascinating as its subjects are.