Frode Gjerstad Credit: courtesy the artist

Frode Gjerstad once explained the concept of his group Detail as “too free for the jazzers and too jazzy for the improvisers.” The 69-year-old Norwegian reedist, who currently favors alto saxophone and B-flat clarinet, has struck that balance throughout his career. Gjerstad grew up in Stavanger, Norway, which had next to no free-music scene. He figured out early on that he’d have to get out of town to find like minds, and so he’s developed long-­standing relationships with musicians from Europe, South Africa, and the U.S., including nonidiomatic improvisers (Derek Bailey, John Stevens), free-jazz greats (Bobby Bradford, Hamid Drake), and straight-up noisemakers (Lasse Marhaug, Anders Hana). He’s also been a mentor for younger Norwegian improvisers such as the two who accompany him on his current U.S. tour. Drummer Paal Nilssen-Love began playing with Gjerstad 28 years ago, when he was just 15; bassist Jon Rune Strøm, who’s in his early 30s and plays with Friends & Neighbors and Universal Indians, has been in the trio since 2010. They stand squarely with Gjerstad in his in-between space, propelling his darting lines and scuffed timbres with shifting rhythms, low-end counterpoints, and surges of pure sound. New York trombonist Steve Swell, who plays with the trio tonight, is no stranger to their work. Three years ago he joined the group in Chicago to record the live album At Constellation, where his rubbery phrasing, hushed vocalizations, and intuitive anticipation of dynamic shifts fit right in.   v