On Saturday night a handful of New Haven musicians took the stage at Firehouse 12 on 45 Crown St. with little knowledge of where the night would take them. For most people, this would mean chaos. But for the New Haven Improvisers Collective, or NHIC, this is how they perform.

The Collective got together at the 9th Square venue Saturday night to celebrate the release of its latest album, “Inflection.”

Making “avant-progressive-chamber-pop-jazz” music, the NHIC was founded about five years ago “to give a place for people to get together to create new music,” said founder Bob Gorry, who works as an electrical engineer when not playing electric guitar. Musicians of any level can meet to improvise on the last Monday of every month at Never Ending Books on 810 State St. Anywhere from five to 15 people have shown up for these jam sessions.

Collective improvisation works through interaction. “You can respond in any way to what you’re hearing. Someone does something; you either ignore it or respond to it,” John Venter, one of the core NHIC members, said. Venter plays bass clarinet and various saxophones.

“For me, it’s often not conscious,” said Paul McGuire, another core member who plays saxophones and the djembe. “I’m surprised when I listen back to it.”

The NHIC also hosts open performances for which members “compose” their own music. Composition, however, ranges from merely titling a piece so that other improvisers can interpret the prompt to thinking through the entire concept. Before such a performance, Gorry said, “We get together once or twice and talk about what to do,” including who sings, who cues and more.

Most NHIC members “don’t make a living out of [music],” Gorry said. Members are not only diverse in experience, but also in age. Though McGuire admits, “Women are scarce.” Regardless, women are featured on both NHIC-produced CDs, which were recorded live at Firehouse 12.

Yale students have also been known to show up to monthly meetings, but, according to McGuire, “Yalies come once or twice but then get really busy.”

Core members of the group make up the hypnotic Erasmus Quintet, focusing on “eternal rhythms,” and Mayhem Circus, playing “lowdown jazz.” Both groups performed Saturday.

The Erasmus Quintet consists of Gorry, McGuire, Adam Matlock on accordion and clarinet, Jeff Cedrone on electric guitar and Steve Zieminski on electronic vibrophone.

The Quintet, named after an 1800s basketball team, was most seductive this Saturday when musicians exchanged sustained high-pitched lines. It felt as if snake charmers were working their magic on the audience. In the absence of a drum set, Matlock added his own percussive charm by clamping his clarinet keys or rapping on his accordion. He even took off his clarinet mouthpiece and played without the body, displaying the versatility of his instruments and interpretations.

The intimate space of Firehouse 12 allowed audience members to immerse themselves in sound. (Famed acoustic designer, John Storyk, designed the space.) As each song wafted between ambient miscellany and locked-in climax, listeners were as unclear about the trajectory of the music as the players were. Beautiful lilting melodies were often interrupted with discordant sounds — accordion and guitar have never sounded this good. The Quintet occasionally whines and squeals, which can get annoying. But, for the most part, audiences will enjoy the ride and be amazed that everything is improvised.

“This is jazz in its loosest sense,” Gorry added. “In jazz, you know the rules.” The NHIC highlights the improvisational nature of traditional jazz, but deviates from the Real Book standards of tightly structured heads and bridges.

Perhaps what makes the Erasmus Quintet endearing is the group’s sense of humor. On Saturday, Cerone started a piece by announcing the title: “I am not the sun, but a ray of light and a bird’s tear.” The Quintet even performed a song dedicated to David Foster Wallace’s “Infinite Jest.”

Though it was easy to draw similarities between pieces of the group’s improv and popular music, the NHIC’s sound is hardly classifiable.

NHIC’s music has a “niche market,” Gorry admitted. “People who show up like adventurous music.”

To follow NHIC, or buy their CDs, visit www.nhic-music.org.