The days are starting to grow noticeably shorter in the Pacific Northwest, and the end of the month-long Seattle Chamber Music Society Summer Festival brings yet another wistful reminder that we’re now facing the season’s inexorable downward slope. An immersive atmosphere of four weeks of three concerts each (plus free prelude recitals and additional events) gives the festival much of its flavour, making one all the more reluctant to bid adieu.

It’s been a month especially generous in discoveries, from the world première of an imaginatively crafted single-movement piano trio commissioned from Derek Bermel (with the Saramago-inspired title Death with Interruptions) to a welcome dose of vocal chamber music gems and other rarities mixed in with more standard fare.

On Saturday night the festival drew to a close with a typically diverse roster of musicians (totalling 15 over the course of the concert). The programme was similarly abundant in scope, establishing a somber tone at the outset with Mozart’s String Quintet in C minor (K406). Originally conceived as a serenade for wind octet (K388) — imagine this score as a little ‘night music’ for a celebratory occasion! — K406 features a remarkably shadowy palette in its guise as a string quintet not only by virtue of the tonality but thanks to the relationships Mozart exploits  between the pair of violins (Emily Daggett Smith and Erin Keefe) and the two violas (Michael Klotz and Roberto Díaz) and cello (William De Rosa).

Díaz’s instrument in particular brought out a dark, woody sonority from Mozart’s rich inner voices. The ensemble balance worked well as a whole, and the commitment of the players was obvious, but there was little risk taking. Their subdued approach was a mixed blessing, for example, when it came to the severity of the canon writing in the minuet: overlapping lines were shaped with clarity, yet the rhythmic impulse felt undercharged. A homogeneity of accent and volume likewise smoothed over the pathos of the outer movements.

Nothing could be called tepid, however, in the account of Beethoven’s Op.20 Septet in E flat major which followed. Presented on the composer’s first-ever benefit concert in Vienna in April 1800, the Septet enjoyed so much success throughout his lifetime that Beethoven famously came to resent its popularity. (It was also the composition he chose to introduce his name to London audiences.)

For this occasion, four principals from the Seattle Symphony — bassoonist Seth Krimsky, horn player Jeffrey Fair, cellist Efe Baltacıgil, and double bassist Jordan Anderson — teamed up with Ricardo Morales (clarinet), Ida Levin (violin), and Geraldine Walther (viola) to create an ensemble that danced, charmed, and occasionally rollicked like a roadster on a joy ride across its six-movement span.

The Septet’s more festive outbursts put one in mind of a pleasant summer fairground, which isn’t so far-fetched given the work’s wind serenade heritage. Beethoven opted for single rather than the usual double winds, thus allowing for an enchanting parade of changing timbral combinations and solo spotlights. Indeed, a good deal of the Septet’s ‘content’ resides in just this interplay of textures, with individual members of the ensemble emerging into the foreground — Fair’s golden-toned fanfare to spring the Scherzo into action, or Krimsky’s stylishly phrased bassoon line in that movement’s trio, among myriad examples.

At the same time Beethoven allots starring roles to the violin and clarinet. Ida Levin infused her part with zesty personality, embracing its motley character, whether in the blissful flights of the Adagio or the finale’s extensive cadenza. Pouring out his honeyed song in the Adagio, Ricardo Morales (heard earlier in the week in a touching performance of Mozart's K. 581 Clarinet Quintet given in one of Seattle's parks) made it impossible to dismiss the Septet as a trifling entertainment against which Beethoven the innovator must be measured -- which is exactly how some critics treat the piece, taking their lead from the composer's own regrets.

But the exuberant spirits which bring the curtain down on the Septet were sent into exile, following intermission, by the single work filling the programme's second half. Tchaikovsky balked at the proposal to write a piano trio, and when the death of his mentor and friend Nikolai Rubinstein in 1881 at last provided the impetus, he nonetheless cast his sole foray into the genre on a scale that sounds like a grand concert work arranged for reduced forces.

Dedicated “to the memory of a great artist” (an intentional echo of Beethoven's inscription of the Eroica “to the memory of a great man”?), Tchaikovsky's two-movement Piano Trio in A minor traces the path not of heroic idealisation but of elegy and fantasy. Curiously, the very same trio of musicians had undertaken the Op.50 Trio during one of last summer's concerts (I wasn't present for that occasion), but midway through they were forced to abandon the performance when a menacing smell of smoke sent the audience heading for the exits; the auditorium cleared out, although the source of the fire was discovered be outside the building.

This time their account of Tchaikovsky's Trio generated enough passion to set off the recital hall's entire system of alarms. There was much to admire in violinist Andrew Wan's ability to convey raw emotional power without compromising his gorgeously silken tone; his muted instrument added a sense of foreboding to the lamentation of the second movement's ninth variation, like Orpheus beginning his descent. Cellist Julie Albers enraptured with her untiringly imaginative phrasing and depth of feeling, etching gestures of mourning into the long arching lines of the funereal first movement.

At the keyboard, Adam Neiman played from memory, freeing himself up to shape a phenomenal performance that encompassed volcanic torrents of grief and dazzlingly nuanced sonorities (particularly in the widely spanning spectrum of the second movement). Tchaikovsky wrote the part as a quasi-piano concerto, so substantial is it, embedding a memorial for Rubinstein the pianist within his larger memorial. At the outset of the massive variations movement, for example, Neiman elicited subtly varied emphases of rhythm in the main theme's repeated phrases, as if to signal in advance the life-affirming cycle of invention and imagination that fills this movement.

Yet the Trio concludes with a devastating return to the funeral idea of the opening. I couldn't help thinking that, as in Tchaikovsky's Pathétique Symphony, a simple reversal of order – the Trio in the middle, the Septet as as 'last dance' – would have altered the character of the entire programme. And as an elegy, this was a particularly moving choice to bring the festival full circle and invoke the memory of Toby Saks, the Chamber Festival's founder and guiding spirit for decades, who died soon after the festival closed last year.