As these lazy August days dwindle, peak and pine, Santa Fe music-mavens can’t be faulted for feeling 1) a bit sad that the crazy summer festival scene is nearly finito and 2) a bit sated with the hyper-giddy whirl of chamber music concerts, operas, chorales, recitals, et al., that have kept the Villa Real rocking along for the last couple of months. So count us impressed when a mostly lighthearted program arrives to cheer the spirits and mark a madly upbeat beginning of the end.

Such as, for example, the Santa Fe Chamber Music Festival's concert on Aug. 11 at St. Francis Auditorium: Mozart, Haydn, Mozart, Weber. The previous week's spate of commissions and brand-new music just past, SFCMF powers-that-be laid on, for starters, Mozart's gracious String Quartet No. 21, K 575, in the sunny key of D. The Johannes Quartet got off to a ragged start—intonation issues—but soon settled into a crisp account of this elegant, deceptively simple quartet. The cello plays a major role here, and Peter Stumpf delivered the goods.

The other piece of Mozartiana, his Duo No. 1, K 423 in G, another cheerful key, is full of little surprises and busy invention. We heard a full-spritz-ahead reading from Ida Kavafian, violin, and Steven Tenenbom, viola. Jolly times persisted with Weber's exuberant Clarinet Quintet, Op. 34, with David Shifrin and, again, the Johannes players. A sort-of concertino with string accompaniment, the piece leaps and bounds happily along with scarcely a thought in its pretty head, while presenting plenty of challenges for the soloist. Shifrin's brilliance, seemingly effortless, just took all that pianissimo passagework right in stride.

The darker side of the evening had been Haydn's dramatic solo cantata, Arianna a Naxos, with demands for brilliance of another sort from its tragic protagonist. The tale of Ariadne, marooned on Naxos—sola, perduta, abbandonata—by her faithless lover, Theseus as he headed for Athens and greater glory, has inspired, among many, many settings, Monteverdi's lost 1607 opera L'Arianna and Strauss' 1912 Ariadne auf Naxos. But midway between these two, in 1789, Haydn had his own way with the sad princess. The cantata, here sung by Sasha Cooke with Pei-Yao Wang at the piano, alternates between lamentation and accusation in a pair of extended recitatives and arias. Cooke made Arianna a desperate victim, her rich, creamy mezzo embracing the heroine's anguish with conviction and gorgeous velvet legato. Her hell-raising furioso F minor finale to the second aria would simply have incinerated that odious Grecian churl.

Plenty of us hausmusik fans had circled and recircled Aug. 14 on our summer concert calendar as the date for (arguably, please) the SFCMF's must-hear program of the season. Believe me, 'twas even so. The first of only two works on deck, Mozart's E-flat Major Divertimento, K. 563, stands unique in the composer's canon on several counts: It's his only string trio; it's his lengthiest piece for small chamber ensemble; although a towering achievement from one of his most productive periods, it's infrequently performed.

Oddly denominated as a divertimento, the work is anything but the trifling pièce d'occasion one generally associates with the term. With all repeats taken, this trio can occupy the better part of an hour. The first two movements alone account for nearly half that time. K 563 brings to mind the kind advice of Lear's Edgar: "Ripeness is all." As a coda of sorts to Mozart's final quartets and quintets, grandly scaled and packed with invention, the trio presents the God-beloved composer at his ripest.

Stumpf plus Kavafian and Tenenbom, 50 percent of the ensemble OPUS ONE—now in business at the Music from Angel Fire fiesta—offered a richly ripe performance as well, a combination of elegance with eloquence. In the Adagio movement, they touched upon tragedy, maintaining a pensive fluidity throughout its heavenly length. The two trios of the second minuet rocked along like boisterous country dances, and the final Allegro's easy good cheer almost mocked the serious tone of that opening Allegro.

The concert's second half presented one of the irreplaceable, absolutely original chamber works of the last century, Olivier Messiaen's Quartet for the End of Time in a masterly reading. Ran Dank throughout was a pianist of exquisite sensitivity. Cellist Eric Kim's Louange à l'Éternité de Jésus conveyed an ecstasy of adoration. Violinist Jennifer Gilbert, especially in the quartet's final passage marked "extremely slow, tender, ecstatic," the Louange à l'Immortalité de Jésus, soared and sang.

Beyond praise: the young Irish clarinetist, Carol McGonnell. Her imposing solo movement, Abîme des oiseaux, marked "slow, expressive and sad," was all of those things and much more. Messiaen makes extraordinary demands upon the soloist, with dynamics on a single note ranging from ppp to ffff, immensely long phrasing and notation that almost exceeds the capacity of the instrument. McGonnell made it all happen with precision and absolute refinement.

So, speaking of Messiaen, make a note of next August's final SFCMF program for 2015—a blockbuster. Alan Gilbert will be on hand to conduct some 45 artists in Messiaen's massive Des canyons aux étoiles. Expect 90-plus minutes of the most remarkable sonorities you'll ever hear. Expect the SFCMF's most ambitious programming in its 43 years. Expect…well, just expect the most.

The Santa Fe Chamber Music Festival’s 42nd season continues through Aug. 25.