Though the early-music movement in this country is still considered in some circles to be academically quixotic and technically inferior, the Philadelphia debut of Quatuor Mosaïques at the Kimmel Center's Perelman Theater on Wednesday had such musical intelligence and sensual allure that returning to more conventionally hard-edged groups, from the Juilliard to the Emerson Quartet, is no longer an attractive prospect.

The Quatuor Mosaïques members arose from Concentus Musicus at a time (1985) when that group seemed more preoccupied with mastering period instruments than with projecting the music. Nobody gets away with that now, and from Quatuor Mosaïques' many recordings of Haydn, Mozart and Beethoven, you could expect high-level playing. However, the group hasn't often been heard in the United States; the Philadelphia Chamber Music Society, which presented the concert, negotiated for years.

Initially, the in-person Mosaïques represents nothing radical relative to the historically informed revolution in baroque-period music. With further listening, its low-fat, less-aggressive blends of sound simultaneously projected a solid sense of the music's totality while revealing the inner workings. That doesn't happen so often. The blend also gave a particular glow to pieces that ask for surface gloss, like Mozart's String Quartet in C ("Dissonant") K. 485, the minuet from Mozart's Quartet in D minor (K. 421), and Schubert's Quartettsatz (D. 703).

Extra credit for that glow goes to cellist Christophe Coin, who needed none of the usual physical vigor to make rhythmic points, but created his own kind of momentum with pulsating effects that stayed well inside the quartet's overall sound envelope.

Sharp attacks that usually call an audience to attention were mostly eschewed by first violinist Erich Hobarth - they weren't needed. Vibrato-less phrasing can sound woozy to modern ears, though Hobarth was particularly adept at creating a seesaw effect that forcefully propelled one's ears to the next musical paragraph. With its less-imposing sound, the group also made better sense of the starting and stopping in Haydn's String Quartet in F major (Op. 77, No. 2). Haydn knew what he was doing; not until now did I know what he was up to.