"There is no such thing as melody. There is only now." That's according to guitarist Jeffrey Hayden Shurdut, founder of This Is The Music Of Life, "a group of established and emerging multi-instrumental, inter-disciplinary artists dedicated to documenting the essential connection between the visual, movement, music and word in a living and creative space."

Tonight, Shurdut's group combines with altoist and Sun Ra Arkestra leader Marshall Allen, on a co-bill with saxophonist John Tchicai, leading a trio completed by guitarist Mary Halvorson and drummer Ches Smith of Trevor Dunn's Trio Convulsant.

Shurdut's notion, of spontaneity uber alles, of the overriding importance of the current moment, is of course key to free jazz, improvisation, new music, avant-garde or whichever of the myriad terms for this music—all of which bleed over into each other's already imprecise borders—one chooses to use. This idea of the power of the present is especially true in the case of the headliners, two men whose biographies tend to emphasize the past, despite their ongoing ventures into new creative areas.

John Tchicai's name is inevitably followed by mentions of his involvement with John Coltrane's Ascension, his prominence on the 1960s New York loft scene and his pioneering bands the New York Art Quartet and New York Contemporary Five. But many biographies leave off there, neglecting his next four decades of musical exploration.

Partially that's due to the Afro-Danish Tchicai's semi-retreat into northern Europe through the 1970s and into the '80s. But he now splits his time between his primary home in France and California, and since switching axes from alto to tenor in the mid-'80s he has toured and recorded regularly, in a breathtaking variety of settings.

Despite Shurdut's claims to the contrary, melody does exist when Tchicai plays. In contrast to the more fiery, abrasive soloing of many of his contemporaries, Tchicai has always favored digging into a melody and spinning it off into intricate lyrical flights. But his playing and his longtime dedication to the avant-garde, despite (or, more likely, due to) his innate melodicism, proves Shurdut's point another way: These melodies only gain significance when coupled with the emotion of the instant.

Shurdut's own music is tied to his concept of Environmental Tuning—"tuning synchronized to the sound of one's surrounding." Of course, when playing with Marshall Allen he has to prepare himself for a musician attuned to a whole other set of surroundings. Allen has spent the past decade carrying the torch for Sun Ra's outer space explorations, striking a balance between the Arkestra's classic repertoire and his own compositions and arrangements.

But as much fun as the spectacle of a full Arkestra show can be, Allen's talents as a fiery improviser are often better showcased in smaller combinations. At 81, his hands still blur like hummingbirds over the keys of his alto as he tears off brief, emphatic squeals.

"Improvised music appeals to a select group of people," explained Tchicai via e-mail. "It's not a music for the totality of a population, it's for people that are looking for something exciting, something deeper and something out of the ordinary." John Tchicai's gift is in weaving myriad mini-compositions out of an improvisation, delicate fragments with the potential for greater elaboration. His audience, and that of the music being celebrated by both these sets of musicians, consists of those willing to appreciate these for the fleeting moments during which they exist.

John Tchicai/Marshall Allen, Thu., Jan. 26, 8 p.m., $12, The Cinema (formerly CineMagic), 3925 Walnut St., www.arsnovaworkshop.com.