Whether it’s classical composers looking for inspiration, jazz musicians seeking a more formal approach, or rock musicians tapping into whatever seems to work, mixing musical genres is an idea that’s been around for quite a while.

The Danny Fox Trio, a piano-bass-drums ensemble, draws on all sorts of sources in and outside of jazz on its way to music, which proved Saturday night in Portland to be a challenge to the ears but also one that rewarded careful listening. A rather substantial asterisk must accompany any evaluation, however. Leader Fox announced there had been a “mix-up” about the availability of an acoustic piano for the concert. Therefore, Fox was forced to play electronic keyboards for the show.

This changed the group’s sound markedly from its recent recordings and brought it much more into a jazz-rock fusion mode. At times, the trio sounded a lot like Miles Davis’ rhythm section circa 1970, which is not necessarily a bad thing altogether.

Though this trio champions a collective approach, keyboardist Fox takes the lead in composing and, in a sense, conducting the group through the complexities of his musical vision. The emphasis is definitely on theme and variations, with the variations representing everything from prog-rock to minimalist flutters to crashing dissonance, all in the course of a few bars.

On Saturday night, solos would emerge out of the collective interplay and evolve, sometimes taking the tune into new directions that, nonetheless, hearkened back to a central motive.

“Tumble Quiet,” one of a couple of laundry-themed titles Fox jokingly announced, used a pulse set by him as a takeoff point for passages that occasionally became rhythmically unbalanced. “Funhouse Memory” went from a funk beat to explore spooky corners of sound, with drummer Max Goldman scraping his cymbals to produce eerie tones. “Bonkers” went even further out on the edges of tonality.

Undoubtedly a fair number in the crowd at One Longfellow Square were there to see and hear Chris van Voorst van Beest, the bassist in the trio. A Pownal native, he was for many years a fixture on the local jazz scene (often featured in the projects of drummer Steve Grover), before moving on to New York. His solos Saturday were tasteful and his bass lines (even occasionally in a standard walking line) were fundamental to the trio’s sound.

“Wide Eyed,” the title tune from the group’s latest CD, offered a rare delicacy in its match of relatively uncomplicated lyricism with a slow tempo. This group likes to mix it up but knows that a touch of pretty can be welcome.

Though missing a big piece of its usual instrumentation, the Danny Fox Trio still produced interesting music that bodes well for future visits when an acoustic piano may find its way onstage.

Steve Feeney is a freelance writer who lives in Portland.