Was the thunder coming from inside the Gordon Theater on the Rutgers Camden campus or outside amid Saturday night's torrential rain?

Both places. Pianist Di Wu, whom Philadelphia audiences know well from her years at the Curtis Institute and Astral Artists, played Rachmaninoff's Piano Concerto No. 2 with Symphony in C in a performance with a shameless taste for musical gestures of tidal wave proportions. Music director Rossen Milanov seemed to challenge her with big-boned phrasing that asked, "Can you top this?" She certainly did in the third-movement cadenza, which indeed thundered.

Though the composer himself favored faster tempos and more classically disciplined performances, his music has been claimed by recent generations who don't apologize for the resemblance to 1940s Hollywood film music. In the opening moments, Wu served notice that the composer could take a long lunch because she was in charge and taking the time she needed to explore the expansive melodies and lush chords. At times, her hands went out of sync in ways that gave the illusion that the music was impetuously tumbling all over itself.

Any number of passages will no doubt take on great interpretive specificity as she plays the piece more. But the degree of identification Wu had with the close of the first movement told you a major Rachmaninoff pianist is in the making.

Tchaikovsky's Symphony No. 6 ("Pathetique") felt a tad anticlimactic, the piece itself being a tough early-in-the-season assignment for this postgraduate orchestra. Brilliant moments stood alongside mildly ragged ones. Milanov wasn't at his most cogent: When the first movement was slow, it was sprawling. However, the end of the lamenting final movement had incredibly eloquent bass pizzicatos and well-defined rhythms creating closure to music that's almost too tragic to stop.

The orchestra's annual Young Composers' Competition winner was Douglas Buchanan's Malleus, an orchestral work inspired by the Salem witch hunts. Now a student of Michael Hersch, Buchanan shares his teacher's sense of creative imperative: Malleus clearly needed to be written with all manner of orchestral upheaval. Pedal-to-the-metal percussion eventually made way for a humble, hymnlike tune played by the winds, reminding you of the pious bedrock on which this sorry piece of American history was born.

Contact David Patrick Stearns at dstearns@phillynews.com.