All around town with Morty and John.

When Morty Met John? a John Cage/Morton Feldman Festival, Sat.-Sun. Oct. 25-26, at Zankel Hall, 881 7th Ave. (57th St.), 212-247-7800: Cage Sonatas and Interludes, Sat., 3 p.m.; Feldman String Quartet II, Sat., 6 p.m.; Cage Song Books and Winter Music, Sun., 7:30 p.m. At Miller Theatre, 2690 Broadway (116th St.), 212-854-7799: Feldman Triadic Memories, Sun., 2:30 p.m. At St. Thomas Church, 5th Ave. (53rd St.), 212-757-7013 Cage Music for Carillon, Sun., 5:15 p.m. It is excellent planning by the Carnegie Hall and Miller Theatre people to have scheduled the much-anticipated When Morty Met John? festival on the weekend when Daylight Savings ends. As the final whispers of Morton Feldman's Second String Quartet are swallowed by the underground walls of Zankel Hall just after midnight on the 25th, the performers and audience members who endured the six-hour long megawork will certainly be grateful for that extra hour. Indeed, a work that throws the very notion of time and space into question certainly seems to possess a strong synergy with the one day of the year where time is literally suspended.

Beyond issues of time, I have always enjoyed Feldman's painterly, lengthy works best in darkness, with the notes illuminating the space like fireflies and sending waves of velvety blackness through the quiet. The crest of the fall season, as the nights become longer and colder, exude Feldman. The slow changing of color and light that characterizes this time of year reflects Feldman's profoundly intuitive and coloristic signature sound. That the season is simply a part of a larger continuous cycle points to his perception of large-scale structure, repetition and evolution.

Catering to Feldman's eccentric conceptions of time and space are new music zealots the Flux Quartet, who first performed the work in 1999 at Cooper Union and released a recording through Mode Records that can either be listened to as five CDs or as one continuous piece on a DVD format. Their interpretation of this work has already garnered much praise from some of New York's stingiest critics, but they will need to compete with the rumblings of the subway under Zankel, which could add a new dynamic.

But this festival is not only about the Second String Quartet. It is about a moment more than 50 years ago when two great artistic minds first encountered one another. Directed by one of today's most prominent new music vocalists, Joan La Barbara, who was a close friend of Morty's and a longtime supporter of both of their musics, the two-day, five-concert series traces the story of one of the most fascinating relationships in musical history.

Appropriately, the weekend begins with a performance by pianist Margaret Leng Tan of Cage's Sonatas and Interludes for Prepared Piano, a strictly controlled work that dates from 1946-48. Cage and Feldman met in 1949, and this work predates Cage's forays into indeterminacy. Feldman's music from this early period, not included on this festival, was also radically different from the lengthy sound paintings represented here, focusing primarily on short, Webernesque atonal musings.

The rest of the works on the program were written after the fateful meeting and demonstrate the exchange of ideas that occurred throughout the following four decades: Cage's "Solo for Voice 45" from his momentous Song Books engages the singer in a number of musical and non-musical activities; it's performed simultaneously with his Winter Music for Multiple Pianos; Feldman's 90-minute solo piano work Triadic Memories that never exceeds a triple pianissimo dynamic marking performed by New York adventurer Marilyn Nonken; and finally (for the tight-fisted among us) the complete Music for Carillon performed by Miller Theatre director George Steel from atop St. Thomas Church and best heard from the sidewalks of 5th Ave. and 53rd St.

The festival is truly momentous, but if the shear magnitude of the event seems inconceivable to you, perhaps some advice from Cage himself would help: "If something is boring after two minutes, try it for four," he is quoted as saying. "If still boring, then eight. Then sixteen. Then thirty-two. Eventually one discovers that it is not boring at all."