Alternative musical universes aren't the stock and trade of the Philadelphia Orchestra, but that's what audiences were invited into Friday at the Kimmel Center in a concert with two new concertos. They were nothing radical, but they hardly represented the status quo.

The audience seemed perfectly comfortable with it all, partly because the performances under music director Yannick Nézet-Séguin were shipshape, partly because the pieces were hugely engaging, even at their least conventional. Take Maurice Wright's Resounding Drums, for timpani and orchestra, for example.

Though most concertos feature the soloist in the musical foreground, Wright (Temple University's longtime faculty composer) kept principal timpanist Don Liuzzi in a middle ground of sorts, playing an ongoing supporting role within the symphonic textures, but doing so with unusual animation and aggression. Or, as in the first movement, with the underwater grace of a whale. The music only occasionally resorted to liquid musical imagery, but it used all manner of unusual instrumental combinations to create piquant, unprecedented sounds.

The 1529 Siege of Vienna was portrayed in the second movement: Marches had archaic cadences as well as tuned drums that the Turks left behind when their assault failed. The "Singing Drums" third movement was all over the place in a fun though hard-to-parse way, and, in keeping with the rest of the piece, was a wonderful earful.

Jonathan Leshnoff's Clarinet Concerto ("Nekudim") was based on mystical implications found within the Hebrew alphabet, though outside some exotic inflections. The piece was a brooding, lyrical child of the Aaron Copland Clarinet Concerto.

The atmospheric music suggested dark, unfathomable spiritual depths in the first movement. The scherzolike animation in the second movement was full of witty, infectious rhythms. Principal clarinetist Ricardo Morales was at his absolute best, with a steady stream of lustrous but demure tones that made you listen all the more closely.

The new works were framed by Bernstein's Three Variations from Fancy Free and Prokofiev's Symphony No. 7, showing two great 20th-century composers at opposite ends of their lives.

Excerpts from Bernstein's 1944 ballet show how fully formed his personality was at an early age. Many touchstones heard in his later stage works were already there, right down to the Latin music trope that Bernstein later expanded into the giddy comedy of "Conga" in Wonderful Town and "Lud's Wedding" in 1600 Pennsylvania Avenue.

Though dubbed a "children's symphony" at one point, Prokofiev's Symphony No. 7 seems to view childhood from a melancholy distance, if not the wrong end of a telescope. It's the music of a broken man summoning his energies for one last symphony, composing long-breathed melodies unlike the pithier inspirations of his younger years.

At one point in the first movement, Nézet-Séguin slowed the tempo in ways that allowed moments to be both sparkling and devastatingly sad. In contrast, any number of big-orchestra flourishes in the later movements gave the music a subversive edge. One has to look back to long-dead Russians such as Nikolai Anosov to find a conductor with such a strong identification with the piece.

Additional performance: 8 p.m. Saturday at the Kimmel Center, Broad and Spruce Streets. Tickets: $61-$147. Information: 215-893-1999 or