Thursday afternoon’s fifth Chamber program opener brought us a pair of timeless classics, but not ‘til after we’d gotten warmed up with a happy little number by Josef Lanner, known as Die Werber (the suitors). It’s a collection of five brief waltzes preceded by a gypsy dance, arranged here for three violins (Geoff Nuttall, Daniel Phillips and Scott St. John) plus double bass (Tony Manzo). Nuttall dubbed them the “Spoleto waltz orchestra.”

Lanner — known as Vienna’s “waltz king” until the Strauss family came along — packed the piece with bumptious little waltz-tunes of the kind you hear in Vienna’s touristy taverns. Nuttall, as lead violin, did most of the melody work, while his fellow fiddlers and bass player mostly provided the underlying “OOM-pah-pah” waltz beat. It was delightful; they even got the classic “Viennese lilt” just right — and I should know, having grown up in Vienna. Geoff even invited us to get up and dance — though nobody took him up on it.

Before and after, Wadsworth gave Nuttall a good-natured hard time, disparaging the music’s lack of depth and substance — as he’s done in previous programs. He made sure the audience knew that this was NOT his own selection, and that he held Geoff personally responsible for it. “Yes, Papa Charles,” Nuttall responded, muttering to the crowd about how Charles has this way of making him feel like a naughty little kid sometimes. The audience lapped it up like hungry puppies.

With that one out of the way, Papa Charles and company moved on to the program’s musical meat and potatoes, beginning with Francis Poulenc’s amazing Clarinet Sonata. Young Spanish virtuoso Jose Franch-Ballester did the solo clarinet honors, with Wadsworth presiding at the piano. As he told us beforehand, he was there in New York for the work’s world premiere performance in the early 1960’s, with a couple of dudes named Benny Goodman and Leonard Bernstein performing. Boy, the stories this man has to tell! He went on to heap praise on his young clarinet colleague, wheezing “It’ll be wonderful if I can keep up with him” as he settled onto his piano bench.

Anyway, the music was magical. Poulenc wrote in a sensuous, sometimes gritty style — but with endless touches of wit and whimsy, plus suave refinement. The rhapsodic first movement took us through passages of almost painful beauty, with even a spooky moment or two. The central romanza — an aching and pensive lament — gave me goosebumps. The cocky, manic finale included lots of thunder and lightning, with flippant little touches that made us smile. Jose was simply fabulous — and Wadsworth not only kept up with him, but made his Steinway glitter and glow. At 80, his knees might be a bit creaky — but there’s nothing wrong with those fleet and flexible fingers.

From there, it was on to the afternoon’s magnum opus: W. A. Mozart’s deep and atypically depressive “viola quintet” in G minor. As a general rule, Mozart’s intermittent moments of darkness and melancholy never last very long; there’s always a serene or sunny passage just around the corner to keep things in emotional balance. But not so in this stunning work — one of his most profound masterpieces. Our performers were the St. Lawrence Quartet, beautifully augmented by Hsin-yun Huang on second viola.

The almost relentlessly morbid and grief-stricken music made my soul hurt — but in a good way. Great music is always therapeutic — because its universal human emotions are invariably reflected in our own lives. “Wow,” you think. “Even Mozart felt that way?” Or Poulenc? or Mahler? Misery loves company. But shared emotion always leaves you feeling better.

The stormy and “pathetic” (Geoff’s word) opening movement never let up. And, as Nuttall put it, “There are no teacups or powdered wigs in THAT minuet!” The slow movement — with its murky viola mutterings — was played with muted strings throughout, and it simply tore my heart out. The finale started off in the same blue funk. “You just want to go out and shoot yourself,” said Geoff. But towards the end came a final ray of sunshine, in the form of an ebullient country dance. Still, it took me a couple of hours to get over it.