Peripatetic doesn't begin to describe iPalpiti, which gave its annual sensational — and strange — gala at Walt Disney Concert Hall on Saturday night.

On stage were 22 young professional string players, most in their 20s. Behind them were draped flags from the 20 countries from which they came. Presented as the Festival of International Laureates, they have been an ensemble for only three weeks, performing in concert halls and private homes in Encinitas, Aliso Viejo, Beverly Hills and UCLA. The festival ended Sunday with a chamber program at the Los Angeles County Museum of Art.

The ensemble's name comes from the way Italians describe heartbeats. But iPalpiti's palpitations have an unmistakable Russian character, which is a big part of the ensemble's attraction. Assembled as a training program by the Russian conductor Eduard Schmieder and his wife, Laura, iPalpiti becomes, for the few weeks of its existence, the musical equivalent of the tantalizing, palpitating, short-lived musical butterfly that that great Russian writer and lepidopterist Vladimir Nabokov might have pursued.

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The first half of Saturday's program was devoted to the "Hamburg" Sinfonia No. 2 in B-flat by C.P.E. Bach (the most progressive of J.S. Bach's composing sons), a short piece from Webern's student years and a peculiarly vapid "Fantasia on Arias From La Traviata" by a contemporary French composer, Marc-Olivier Dupin. After intermission, Schmieder turned to Tchaikovsky's "Souvenir of Florence."

But forget Florence, Hamburg, the Paris of Verdi's Violetta in "Traviata." The evening's soul was in St. Petersburg.

C.P.E. Bach bridged the gap between his father and Haydn (who was 18 when J.S. Bach died in 1750) maybe more experimentally and entertainingly than any other. He was master of the harmonic surprise, and an enticing touch of anarchy occasionally enters into his forms. Pierre Boulez, while inciting revolution in French modernist music in the 1950s, conducted C.P.E. Bach. Today the composer is the property of early music specialists, who also delight in C.P.E.'s quirks but as quirks of history.

Schmieder, however, palpitates in all he conducts. He did include a harpsichord, but the strings were asked to dig deep, and they marvelously complied with a room-filling richness. C.P.E. became modern again.

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The Webern was big too. His "Langsmer Satz" is a late-Romantic period slow movement from 1905 for string quartet by a 21-year-old who was not yet the miniaturist and harbinger of the post-World War II avant-garde of which Boulez was a leader. Presented, as it sometimes is, in an arrangement for string orchestra, the movement's thick harmonies were more palpitations, but the pendulum was a heavy one. The playing was intensely beautiful.

Then Dupin. What has happened to the French? Born in 1954, a composer who has written some terrible television and film music along with his share of ignored classical pieces, he headed until recently the famed Paris Conservatory — where Berlioz, Saint-Saens, Debussy, Ravel, Satie, Messiaen, Boulez and just about all other great French composers once studied.

Dupin's "Traviata" Fantasia is the setting of familiar excerpts from Verdi's opera for solo violin and strings. The style harks back to Paganini, who died in 1840, archaic even for Verdi, whose opera premiered 13 years later.

There is little fantasy in the straightforward transcriptions of a soprano's lines for the violin, with added virtuosic 19th century touches. It's not even camp, like Franz Waxman's "Carmen Fantasie" (written for the 1946 film "Humoresque"), which was possibly a model for Dupin. In blandness of thought and intent, this is the worst piece I've yet to hear played in Disney.

The soloist was Alexandru Tomescu, an iPalpiti alumnus and now state soloist of Romania. He is a Paganini specialist — and special. He handled the occasional fancy-fingering flourishes and left-hand pizzicato passages with the classy nonchalance of a real virtuoso. He deserves better material.

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A single measure of "Souvenir of Florence," given in its string orchestra version, was all that was needed to sweep Dupin out of Disney. The title refers to Tchaikovsky having composed part of the score in the Italian city, and that has led to the notion of giving the slow movement an easy Italianate lilt.

A new recording of the sextet version by the Emerson String Quartet and two American guest musicians takes a more cinematic approach; sweet phrases are traded off between string players with the grace of Fred and Ginger.

Schmieder instead went for underlying unease, passion touched by the deeper emotions of uncertainly, angst and not pleasure so much as lust for pleasure. He made the first movement arrestingly stormy and treated the slow movement not as a lull but a heavy romance on the rough seas. In the Scherzo, Tchaikovsky alludes to Russian dance. Schmieder contributed the vodka.

The last movement is dangerous. It contains a contagious earworm, a tune that can haunt you for days. In its exuberance, iPalpiti became, here, an agent of infection.

This was an invigorating world-class performance by young players with technique to burn and a palpable desire to live every note.

mark.swed@latimes.com