Guitar aficionados and others came out on Wednesday night to SPACE Gallery in Portland to hear the imposing six-string duo of Nels Cline and Julian Lage, whose appearance here was twice delayed by illness but proved well worth the wait.

Long known in jazz and experimental music circles as an innovator, the self-taught Cline came to wider prominence after joining alternative rock band Wilco about a decade ago. When not engaged with that group or his many other projects, the 59-year-old has been performing with Lage, 27, a former child prodigy and classically trained guitarist who already possesses a lengthy resume of his own in jazz and other genres.

Taking as starting points several compositions included on their 2014 CD “Room,” the pair played an impressive 90 minutes of music that ranged from modern classical sounds through jazz, blues and beyond. Very complex musical structures, free-form improvisations and more laid-back moments shared the program for these players who obviously enjoy their work.

Cline, on a Gibson hollow body electric guitar, generally took the dominant role, while Lage, always very attentive to his partner, would embellish, elaborate and further develop ideas on his Manzer electric. Though they sometimes played in precise unison, it was really in the trading of ideas and development of complementary musical gestures that their communication was most in-the-moment and inspired.

Cline’s “Racy” set the pace early, the leader establishing a labyrinth of notes that drew Lage in. The interplay accelerated until very intense chordings by Cline suggested a finish, only to resolve into another round of scalar development. Combining the use of guitar picks with finger-picking and other techniques varied the listener’s experience of these players’ musical excursions.

Lage’s “Abstract 12” was a brief trip into areas not unfamiliar to fans of contemporary classical music, while Cline’s “Odd End,” displayed the composer’s penchant for time signatures that play with listener’s expectations. A chamber-like piece by the “third stream” jazz composer Jimmy Giuffre was instructive in honoring one of the antecedents of this duo’s cross-genre concept.

“Blues, Too,” Cline’s tribute to the late Jim Hall, got at that legendary guitarist’s way of maintaining melodic simplicity within complex compositional structures. A consonant middle passage within this piece had Lage advancing a lyrical solo on top of a flowing harmonic progression established by the leader. It was a moment that wouldn’t have been out of place in the middle of a Grateful Dead jam. The medley “Freesia/The Bond” similarly took the engrossed audience into very pleasant musical terrain, with welcoming harmonies and sensitive solos leading to a resonant crescendo.

Cline will be back at the State Theatre in January with Wilco, and certainly another show with Lage would make for a most welcome return.

Steve Feeney is a freelance writer who lives in Portland.