Heras-Casado leads the Phila. Orchestra in bold, extreme strokes

Pablo Heras-Casado conducted the Phildelphia Orchestra for the first time Thursday night.

Not long ago, a member of the Philadelphia Orchestra's leadership wrote me with an insight. In talking to musicians after concerts, he had gleaned that interpretation came from the musicians themselves, and not the conductor - and in fact the orchestra was able to play brilliantly without any podium guidance at all.

The idea that a conductor could stand in front of an orchestra and have little or no impact seemed especially fanciful Thursday night during Pablo Heras-Casado's Philadelphia Orchestra debut in Verizon Hall.

Whereas Nikolaus Harnoncourt, just to cite one conductor, would heed the inner beat of Mendelssohn's Symphony No. 3, the "Scottish," straying only here and there to make a point, Heras-Casado took a particularly fluid view of tempo. In the first movement, he let momentum flag, then took off like a shot when the music changed character at the assai animato section. Very animated, to be sure, as the score asks. But within the designation, there's a range. And often, throughout the entire piece, the 38-year-old conductor made a fair number of rather extreme tempo changes.

Why? To the extent that a brief tempo change here or there can emphasize a dramatic moment, or a longer tempo change might reveal detail otherwise overlooked, the strategy can bring insight. I wish I could say revelations emerged. But if they did, they escaped me, and I often found myself wishing for the terra firma of a more judicious approach.

There's been a lot of talk for years in the orchestra world of the need for new concert formats, but this was one to comfort traditionalists (who nearly filled the hall). Violinist Akiko Suwanai performed Prokofiev's oft-programmed Violin Concerto No. 2 in G Minor, leaving any element of newness to Tchaikovsky's Fantasy-Overture, The Tempest, Op. 18. The novelty aspect is that here are sounds - the shifting harmonic changes (an unsettled, otherworldly sea) - that might appear nowhere else in Tchaikovsky. The ensemble, while not as vivid as it might have been, was largely on solid ground.

Suwanai began the Prokofiev with a bold sound, a promise only partially sustained throughout the piece. She did not exhibit the kind of variegated approach to colors for which one might have hoped. The violinist was, however, unfailingly assured and polished.

Additional performance: 8 p.m. Saturday at the Kimmel Center, Broad and Spruce Streets. Tickets: $10-$110. Information: 215-893-1999 or www.philorch.org.