If you attend festival performances regularly, it can be easy to overlook the magic that makes them succeed or, in its absence, fail. By nature, most festivals present ensembles built of musicians who have flown in from here and there, some of whom have worked together before, many of whom have not. And with just a handful of rehearsals, they are expected to produce a performance that sounds as if they had been playing together for years.

They do have a conceptual safety net. If they don’t quite reach that goal, listeners who understand the ad hoc nature of these ensembles are often more forgiving than they might be if they were hearing a full-time string quartet or piano trio. And the repertory that chamber festivals thrive on – piano quartets and quintets, mixed-timbre septets, not to mention new works – is such that comparisons with established ensembles are hard to come by.

All that came to mind on Saturday evening, when the Portland Chamber Music Festival opened its second concert of the summer with a performance of Mendelssohn’s String Quintet No. 2 in B-flat major (Op. 87) that was so carefully shaped and full of phrasing subtleties that no rationalizations about the nature of one-off readings were necessary.

Mendelssohn deserves a lot of the credit, of course. Like so much of his music, this quintet is so melodically rich, and harmonized in ways that are at once comfortably assuring and sufficiently idiosyncratic to sound fresh, that musicians find it as seductive as listeners do. The ensemble here – violinists Anna Lim and Gabriela Diaz, violists Jessica Meyer and Melissa Reardon, and cellist Trevor Handy – gave it as focused, energetic and polished a performance as you’re likely to hear.

Much the same could be said for the reading of Elgar’s Piano Quintet in A minor (Op. 84), which closed the program, although here the musicians had to work harder to keep listeners involved, since the piece itself is considerably longer than it is interesting.

It is not for nothing that Elgar’s symphonies, and works like the “Enigma” Variations or the Cello Concerto are far better-known than the Quintet, which Elgar sheathed in a variety of treacly Romanticism that was already past its sell-by date. (True, the orchestral works have some of that too, but they are also more muscular, and they better honor the line between the beautiful and the saccharine.)

To be fair to Elgar, the piece was composed in 1918, during the final months of World War I, when Elgar, depressed by the war’s carnage, was undoubtedly trying to find a musical lifeline in a style that reached its apogee before the turn of the century. And the piece does have its charms, not least an Adagio in which a rich, climbing theme is elaborated on by each of the five instruments. The musicians here – Diaz and Riordan were joined by pianist Henry Kramer, violinist Jennifer Elowitch and cellist Brant Taylor – gave a performance that was beyond reproach, but in the end, it was still the Elgar Quintet.

Between the Mendelssohn and the Elgar, clarinetist Benjamin Fingland played Mario Davidovsky’s “Synchronisms No. 12″ (2006), the latest entry in the “Synchronisms” set that the composer began in 1963.

For me, the Davidovsky was this concert’s main draw. Though it lasts only seven minutes, it uses the clarinet’s full range, and is packed with demanding, athletic figuration that test a player’s agility without becoming empty display – and also without dwelling on the honking mutiphonics on which so many contemporary clarinet works are built. And its electronic component is appealingly spare, a blend of alternately wooden and metallic percussive timbres, as well as buzzes and pings that sound entirely computer-made, but are actually built of samples from acoustic instruments (including the clarinet).

One challenge of a piece like this, as Fingland noted in his introductory remarks, is that the electronic sounds are fixed and inflexible: They don’t react to what the clarinetist does, as live musicians would. But Fingland wove his clarinet line into the texture so vividly, and with such a carefully calibrated mix of virtuosity, warmth and even humor, that the performance sounded interactive, as if it were played by a live ensemble.

Allan Kozinn is a former music critic and culture writer for The New York Times who lives in Portland. He can be contacted at:

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