At the Guarneri Quartet's designated last Philadelphia concert after 45 years as one of the country's name-brand chamber ensembles, both emotions were appropriate in the extreme. Though the Friday-night program of Beethoven's String Quartet Op. 127 and Schubert's Quintet in C Major could hardly have gone better - whew! - cellist David Soyer's carriage was as labored as his playing was beautiful.

"Don't go through this for our sake!" was my first thought as he entered the stage, his cello seeming to weigh heavily upon him. But the reward was a Philadelphia Chamber Music Society audience that behaved like overheated rock-concert fans.

Sentimentality was warranted. Several group members met at the Curtis Institute; all were nurtured at the Marlboro Festival. Since 1986, the society has presented the group 35 times. Soyer departed in 2001, quoted as saying he didn't want to die in a Holiday Inn after eating at Howard Johnson's. Such is the life of a string quartet.

The others soldiered on, with lanky Arnold Steinhardt always seeming too big for his violin, second violinist John Dalley looking like he's sitting down to a wonderful meal, violist Michael Tree seeming grave and deliberate, and cellist Peter Wiley suggesting the conservative son of idiosyncratic parents.

Pinpointing a departure date is a nest of conundrums. Music-making benefits from accumulated wisdom, but the performers' ability to project that wisdom is unpredictable as time goes on. You can be all you were on one day and so much less the next. Pianists are protected by the magnitude of their instruments; even so, Menahem Pressler's Beaux Arts Trio farewell last season went well here but not in New York City, I'm told.

String quartets are supremely vulnerable. The violin is such a relatively small piece of wood that what comes out of it is defined by who is playing it. Beethoven's Op. 127 came out like a chipped vase on Friday; everything was there but shaky, a reminder of Guarneri disappointments in recent years and why this farewell was overdue.

The quality of the playing has been an issue, but the bigger one is phoned-in performances. Even in the best years, the quartet's playing has never been the sort to reveal the players' inner selves. That impersonal impression was intensified by the 1989 documentary film High Fidelity, showing the players checking into separate hotels to get away from each other. In later years, performances seemed to grow more detached.

Audiences kept coming back for the warmth of tone that was built from the inside out, with an unusually strong presence from second violin and viola, but with soft attacks and releases. Steinhardt's leaner tone defined that cloud of sound with a laserlike precision. On good days, like Friday, he crystallized the music's emotional content with greater-than-usual detail rather than just revealing the formal construction of the music. At the bottom of the sonority, Soyer was felt as much as heard - elegant, concise, and with little apparent physical force.

Such qualities were perfect for the Schubert, which is all about rich, entrancing vertical harmonies changing from intense light to darkness on the alteration of a single note. Also, its double cello instrumentation accommodated Soyer's return without displacing Wiley.

The smartest decision was a lack of encore. The audience would've been happy to have the Guarneri play all night. Best not to risk sullying the memory of Schubert, whose most sublime piece, in any case, can't really be followed by anything. That's another place where accumulated wisdom kicks in. Contemplating Beethoven's spiritual depths is laudable, but so is knowing, after an overdue departure, when to stop.