What is a chamber orchestra? I was asked that question more than once during a week that included local performances by the Israel Camerata and the New European Strings. Perhaps the best example of the classic chamber orchestra is the Israel Camerata, conducted by Avner Biron, featuring Claude Frank as piano soloist. Their performance last Saturday night was very much the best and most polished offering to date in the Ryman’s new chamber music series. The group was composed of quartets of first and second violins, violas, and cellos; pairs of basses, horns, bassoons, and oboes; and a lone flutist. It was very apparent that the average age of the group’s string players, many of whom are Russian émigrés of great experience, put them a full generation ahead of the winds, all of whom looked (and sounded) as if they were scarcely out of the conservatory.

Biron lead a reading of Boccherini’s Symphony in d minor “La Casa del Diavolo” that was notable for its ensemble precision and for its almost choral approach to phrase. This is a work filled with tricks made famous by the Mannheim composers—notably the “rocket,” an orchestral crescendo on an ascending scale, and the onomatopoetically named “roller,” with its rumbling bass line. The Camerata’s strings made these tricks seem as fresh as if they had been discovered yesterday. The cellos and double basses were particularly fine at providing steady support, with the superb acoustic of the Ryman allowing them to be heard to glorious advantage.

While I’m mentioning those cellos, let me say that this is one of the finest cello quartets I’ve heard: Their sound complemented each other; there was no trace of the wolfiness, or upper harmonic dissonance, that I’ve come to expect from cello ensembles; and they even managed accurate group intonation in the cello’s notoriously off-pitch high register. This was particularly important in the second movement of the Boccherini, in which the cellos added particular heft to the music’s “Mannheim sighs.”

None of the gracious playing in the first two movements, however, could prepare the audience for the “terrors of hell” finale, after which the symphony is named. The flexibility of the Israel Camerata here was crucial in conveying the emotional rush of the music. Ritards were rock-steady, crescendos had real punch, and the tension in the softest passages was palpable. There was great concentration and extreme accuracy in the masses of running notes that send a shiver through this music. As far as the strings were concerned, it was masterful.

The contribution of the winds, however, was a problem. Even in sections where they were supposed to come to the fore, they were shrinking violets. This was a particular problem that spoiled an otherwise fine program-closing performance of the Schubert Symphony No. 5 in B Flat Major. More than in the Boccherini, the Schubert requires the color of the wind band to bring a sparkle to the music. But only in the “Menuetto” third movement did they make a bid to contribute to the ensemble sound. By then, however, most listeners had given up hope of even hearing them.

Nobody attending the Israel Camerata’s concert could say they didn’t get their money’s worth. In addition to these two symphonies and some shorter works, pianist Claude Frank joined the group for a very workmanlike performance of Mozart’s Piano Concerto No. 17 in G Major, K. 453. Not one of Mozart’s more spectacular piano concertos, it is nonetheless a work of great suavity in its outer movements, and it boasts a bonus of moony emotion in the middle movement.

Frank very accurately conveyed these excellences in his work. There was nothing heaven-storming here, but the ornamentation was accomplished. His caressing trills were particularly well done, and in the finale I admired the way in which he slowed a tempo too fast for his comfort without causing the music to bog down. If Frank did not display the conscious phrasing of a Murray Perahia, he did much better by Mozart than the recent performance by Peter Serkin (who, I failed to tell readers, performed the composer’s Piano Concerto No. 21 at the NSO’s concert pair a couple weeks ago).

As to the other works on the Israel Camerata’s program, the performance of Puccini’s I Crisantemi and Kopytman’s “Kaddish” for violoncello and string orchestra were merely acceptable. The Kopytman piece found cello soloist Oleg Stolpner indulging in a quick, wavery vibrato that suggested the vocalism of Snow White, while the music itself was too reminiscent of Shostakovich and Bartok to have any real individuality. The Puccini number was the one element of the concert in which the strings did not do well. The ensemble was plagued by ragged attacks, and halfway through it lost its melancholy sweetness. By the end of the concert, I was left with the impression of a group that managed balances better than storm.

Storm, however, is at the heart of Peter Tchaikovsky’s Souvenir de Florence, the string version of which took up the last half of Thursday’s Vanderbilt performance by the New European Strings. This is music with the emotional power of a black hole—it sucks in the listener from the first bar and never lets go. Tchaikovsky originally wrote this for a string sextet, and, truth to tell, this chamber version lacked the edginess of the original. But it did offer a blacker depth, thanks largely to the cantante style of bassists Boris Kozlov and Sergei Akopov.

The group was led by violinist Dimitri Sitkovetsky, who also did the arrangements of both works featured at the concert. In the Tchaikovsky, Sitkovetsky’s ability to manage emotional surge was outstanding, but this is not to say that his take on Tchaikovsky was all external angst. The second-movement pizzicati were delivered with great subtletly, while the interplay between the first and second violins in each movement was Wimbledonian.

One of the performance’s most technically virtuosic moments came in the fugato elements of the finale. Performances stressing this work’s fire and tears frequently break down here, but Sitkovetsky’s string orchestra was prepared. The other half of the program was an arrangement of Bach’s Goldberg Variations, so no fugue of Tchaikovsky’s caused any demur.

As to the Goldberg Variations, Sitkovetsky’s cunning orchestration certainly put them beyond the category of “baroque soporific.” (The now discredited story about this piece is that Bach wrote it for a pupil to play for a sleepless patron.) Sitkovetsky’s take on the music demonstrated not only the range of Bach’s music, but the extent to which Bach was indebted to other great composers of his age. In this one piece, there are variations that exactly mirror the style of Bach’s trio sonatas, variations that sound like studies for the harpsichord concerti, and variations that sound like a seventh Brandenburg.

The real ear-openers, however, are variations that suggest the pomp and splendor of Handel and Telemann, the brilliance of Rameau, the programmatic qualities of Vivaldi, and the tight construction of Corelli. Throughout the performance, the most complex passages were rendered simply, and the simplest passages were revealed to have exquisite complexities. Some of the best moments came during these “simplicities”—trio sonata-like passages that featured violinists Sitkovetsky and Mikhail Rappaport with violist Ron Ephrat and cellist Kati Raitinen. In the end, it was clear that both the audience and players agreed that this was an exceptional performance.

As to the query of what makes a chamber orchestra, I never gave my questioners a straight answer. The concept of a chamber orchestra is too fluid to define—it was certainly hard enough to pin down at these concerts. And for those still seeking an answer to the question, just wait until you hear some of the other chamber orchestra concerts coming up. On Feb. 23, there’s the Nashville Chamber Orchestra performing John Mock’s new Celtic piece at Caffé Milano, and on Apr. 11 the Ryman presents the Orpheus Chamber Orchestra. When you hear these two ensembles, you’ll be even more confused.