Years back, the Philadelphia Orchestra could be said to have many wonderful qualities, but rhythm wasn't among them. A holdover from Eugene Ormandy, who couldn't conduct complex meters? Whatever.
The local debut of Mason Bates' symphonic ricochet Alternative Energy sprang forth in all of its multilayered physicality Thursday, maybe with the orchestra seeming to speak a second language at various rhythmic points, but still making listeners love something they didn't previously know.

Verizon Hall was nearly full, based on the appeal of Russian pianist Daniil Trifonov. But earlier in the concert, Alternative Energy delivered a feast of sound. Six speakers sent electronic effects bouncing around the orchestra, engineered by the onstage composer. And though some conductors zero in on the Stravinskian dissonances, music director Yannick Nézet-Séguin was more interested in Ravel-like blends invited by the rich orchestration.
Musical gestures sprang out every which way, turning multiple colors in a matter of seconds but with a kind of rhythmic bedrock that created a solid frame for first-time hearers and a point of departure for deeper aural investigation. What that investigation revealed was a lovable lack of rigor.
Each of the four movements meditates on a different era of energy consumption, starting with Henry Ford's mass-produced automobiles and ending centuries into the future, when climate change has turned Iceland into something tropical. But the subtitles of each movement really get you only 40 percent of the way into the music. Elements spill over between the seemingly self-contained movements, not just thematic ones: Though only the third movement has a Chinese subtext, Asian elements run throughout the piece.
Never is the music weighed down by its agenda. The dark third movement, for one, evolves into a sort of mutated dance club rhythm that's disturbing, I suppose, but also made infectious by the composer's giddy sense of invention. The only letdown, for me, is the final movement: It goes for simplicity but doesn't cover much new musical ground.
Beethoven's ballet Creatures of Prometheus (excerpts) began the program and Liszt's tone poem Prometheus ended it in a programmatic theme that was nice to think about on the way home. But while there, Trifonov's performance of Mozart's Piano Concerto No. 9 was happily lacking the expressively opaque, trancelike playing of his recent Perelman Theater recital.

Russians have rarely been paragons of Mozartean style, and Trifonov definitely played the concerto on his own terms -- welcomely. Every phrase played off the previous with an endless variety of color and touch in the first movement. The pianist veered into the Chopin zone in the second movement, maintaining elegant finger work but suggesting that 21-year-old Mozart had much anguish to impart. Trifonov made the final movement both sparkle and crackle -- with Nézet-Séguin always there with an answer or argument that put the pianist's ideas in higher relief.
The program will be repeated Saturday and Sunday at the Kimmel Center. Information: 215-893-1999 or