The Guarneri Quartet is no more, and yet there it was (plus one), closing the Philadelphia Chamber Music Society season Friday night. You couldn't fool the audience at the American Philosophical Society, which greeted the four former members of the quartet with love obviously rooted in the years between 1964 and 2009, when the Guarneri was a real force.

They met at Marlboro Music, the Vermont school and festival that is PCMS' sister organization, and the clubbiness surrounding both groups cuts both ways. Most often, relationships nurtured at Marlboro land happily on stages in Philadelphia. Personal attachments, though, also prevent professional detachment, and you couldn't escape the feeling that there were some very good musical reasons for the Guarneri to throw in the towel when it did.

Great moments did surface. With violinist Ida Kavafian in Mozart's String Quintet in C major (K. 515), the second movement was infused with spirit and polish. In the first, however, violinist Arnold Steinhardt broached relatively nonchallenging passages as if arduous. The third movement was a delicate, sleepy affair. And the fourth showed the alpha-male qualities that made Steinhardt an ideal first violinist, even if total control wasn't entirely within reach.

The violinist was joined by violist Michael Tree in excerpts from Bartok's 44 Duos for Two Violins. Steinhardt had a more robust sound here, Tree solid, as they wended their way through a dancing song, a wedding song, a burlesque that shared something harmonic with Stravinsky, and other short tunes.

Its folk material animated the musicians in a way that didn't play out with as much spirit in Dvorák's String Quintet in E flat major (Op. 97). If you chose objectivity, what you heard was an ensemble that would have some work ahead of it in terms of intonation, shared ideas about phrasing, and other basics. If, however, you sifted the sounds for what the Guarneri once was, those moments were there, too, though perhaps a little too fleeting for comfort.