Harmonically, those parts of the work could have passed for rock. The music was framed in jolting, shifting meters Stravinsky would have appreciated, giving it a complementary historical layer. Subtitled "Concentric Paths," the concerto was oddly unsatisfying in some major stretches. The British Adès, 38, has a compositional voice as concise and trenchant as any today. In his relatively small output - this concerto from 2005 is his opus 24 - he always seems to say something important. Yet if there was a point to be discerned in the long growl of a second movement, I could not detect it. At its end, the violin settled in on a repetitive obsession of tones, while the orchestra died down. Like ending a sentence in midthought.

David Robertson was architect of this Philadelphia Orchestra program. The Adès, after being played by itself Thursday night in an Access concert, was flanked by three other works Friday. Robertson, in his fourth season as music director of the St. Louis Symphony Orchestra, has a beat that looked clear from this side of the podium, but the Philadelphians had difficulty - off and on all night - synchronizing entrances. His Vaughan Williams Fantasia on a Theme by Thomas Tallis achieved its customary dynamic contract and a fairly well-developed expressive line. The most striking thing about it, though, was an acoustical dimensionality that had nothing to do with Robertson, but with an ever-changing Verizon Hall. Concerts have turned into acoustical hide-and-seek as experiments continue on the way to correcting the hall's sound. For whatever reason (No bodies in the conductor's circle? Fewer bodies on stage?), the Fantasia glowed. The sound had presence and an afterlife it rarely has.

The quality didn't carry over into the rest of the concert, though you had to think musicians were hearing each other more clearly on stage, with doublings like the horn-cello one in Sibelius' En Saga as focused as they were. Cleaner trumpet entrances and a less-airy principal flute were among the items for a wish list - can't blame the hall there - and the rhythmic floor of the entire orchestra dropped out in one stretch until oboist Richard Woodhams stepped in to restore order. Ricardo Morales provided the most memorable moments with an old-world clarinet sound molded of incredible control.

I wish I could remember now - it's just been too long - what it was that Riccardo Muti did to make Scriabin's The Poem of Ecstasy sound like a great piece of music. Robertson couldn't quite make the justification for an agitated ambiguity that took more than 20 minutes to resolve.

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