Elliott Carter’s prodigious output in his ninth and tenth decades has been one of the phenomena of contemporary music — works of non-stop, all-encompassing inventiveness, with an unflagging ear for drama and color, an uncanny nose for a subject, and a eye open to innovative form. And over 35 seasons as director of Monadnock Music, James Bolle has been one of Carter’s most ardent advocates, offering American and even ( " unofficial " ) world premieres.

Two weeks ago, Bolle led a contemporary program that featured two of Carter’s most ambitious recent works: the Clarinet Concerto, from 1996 (when Carter was only 88), and last year’s ASKO Concerto (named after the Dutch chamber orchestra that commissioned it). Then Bolle’s concertmaster, Ole Bohn, played Statements (he performed the American premiere at Monadnock two years ago), the eloquent three-and-a-half-minute solo-violin piece Carter wrote for him (and dedicated to Aaron Copland), in which the high rhetoric of certainty (slashing double stops) alternates with passages of exploratory and questioning lyricism. Bohn then played the even shorter, quieter, yet longer-lined and quicksilver Rhapsodic Musings, which was dedicated to Robert Mann, former first violinist of the Juilliard Quartet, another group devoted to Carter.

These late works are astonishingly mercurial, constantly changing in tone and color, rejecting the comfort of complacency. If they aren’t exactly easy, or — as the buzz word has it — " accessible, " they rivet you with their shivering immediacy. Carter’s fast movements leave you breathless with exhilaration — or terror; his haunting, seductive slow movements move you to tears — and beyond. In the Clarinet Concerto, the orchestra explodes (the birth of the universe?), then shatters into musical shards that form discreet instrumental constellations (unpitched percussion, muted brass, strings). Daylight bustle — or catastrophe — turns (on a dime) into nocturne, Carter’s ever-deepening sense of quietude and mystery.

The particular drama of the Clarinet Concerto consists of the interaction between the quixotic clarinet hero and each of the various groups — beginning with an implacable fusillade of percussion that occasionally reappears, all the scarier for its understated insistence. Each sequence ends with or gets interrupted by a powerful chord that intrudes like the striking chimes of a cosmic clock, like Auden’s " Time, " which " watches from the shadow/And coughs when you would kiss. "

When the Clarinet Concerto had its East Coast premiere, at Tanglewood in 1998, BSO clarinettist Tom Martin actually moved from group to group, as Carter asks. Monadnock’s superb Steven Jackson never left his place center stage, yet I still felt how in each section — nervous or excited, languorous or searching — he was like Gulliver reaching a new island, a new population with its new set of challenges. In the slyly syncopated conclusion, the clarinet gets the brief last word: " I’m still here. Period. "

The ASKO, a " concerto for orchestra, " has no individual hero. Each player is his or her own hero, finding and making small connections (duets, trios, a quintet) and surprising alliances (piccolo and trumpet; bass clarinet and trombone with velvet cello), though always temporary, each instrument eventually going its own way in its own sweet time. The concerto ends with a spectacular comic turn (comic as in Samuel Beckett or Buster Keaton), a touchingly dithering — and brilliantly difficult — solo for bassoon (bravo, Stéphane Lévesque).

Bolle had a particularly impressive ensemble this year, and he led it in vivid collaborative performances of vibrant energy and clear, sharp definition. A derailment in the middle of the ASKO Concerto, when the conductor’s score fell off the stand, momentarily threw off the pace, but recovery came quickly.

Everything after the Carter seemed to come from lesser musical spheres. In Mario Davidowsky’s Synchronism #9, Veronica Kadlubkiewicz’s live violin interacted elegantly with sound engineer David Hadaway’s expert manipulation of the glamorous pre-recorded soundscape: splintering, tinkling, rippling (like some of the sounds Carter was making with live piano, harp, and vibraphone). But even Carter’s pared-down violin solos take you on a psychological ride; in the Davidowsky, you marvel at the rainbow colors but the train never leaves the station.

In young composer Mark Kuss’s The Show, a joky setting of passages from Donald Barthelme’s allegorical pageant, evidently excerpted from a piece he wrote for the New Yorker on Modernism, baritone James Maddalena declaimed and intoned the text with reverberative splendor ( " We did cereal music with its raisins of beauty — raisins of beauty " ). The Overture, reprised several times throughout the piece, recalls the Russian fair in Stravinsky’s Petrushka. A piano trio plays Brahmsian variations on the Stephen Fosterish theme for the Oscar Mayer wiener commercial. At one point Maddalena erupts into a wild alphabetical " List of Fools, " a Gilbert & Sullivan patter song with words by Kuss: " We settled for: boors and beefheads and barmies and bumkins and babies and boobies and clowns. We had charlatans, do-dos and dullards and daredevils dum-dums and churls in white gowns. "

The text includes Emily Dickinson’s " The soul selects her own Society, " almost complete except for the (I assume) deliberate misquoting of some key words (chariots " parking " at her gate instead of " pausing " ) and the repeating of others ( " unmoved, unmoved, unmoved " ). I guess the idea is to undercut or undermine the very authority of language, or music, or art. But the ironies are over-easy. The " show " of the title seems to be Life Itself, which can never completely satisfy the audience, even as the stakes get higher (the show might close — but, wait!, there’s a promising new volcano about to erupt). I’m reminded of Kafka’s devastating story " The Hunger Artist, " in which the latest popular sensation, the artist who tries to break the record for public starvation, can’t keep his hold on the public. Barthelme’s text seems like Kafka lite, and Kuss’s musical parade of parodies, though entertaining, seems even liter.

Then last week, the 24-year-old Russian pianist Konstantin Lifschitz returned to Monadnock for two Mozart concertos (Nos. 21, in C, and 27, in B-flat — the latter Mozart’s last). The orchestra was startlingly elegant. And Lifschitz plays with a gilded tone. The notes pour out of him. But I wish he hugged the twists and turns of Mozart’s musical/emotional roller coaster as intimately as he caressed the keys themselves. I wish he’d expand his constricted dynamic range. The C-major lacked a certain urgency of phrasing — except in the touchingly tentative short cadenza of the last movement, surely of Lifschitz’s own composing, which evoked the sublime theme of the previous slow movement. Bolle took the last movement of the B-flat at a surprisingly deliberate pace, so the finale didn’t have that startling, mysterious sense of innocent joy and freedom I cherish in this piece. But who could complain about Lifschitz’s trills, or his effortless spinning out of the musical line?

Bolle is such a vivid presence as a conductor, you might forget he’s also a composer. Separating the two Mozart concertos was the world premiere of Bolle’s Clarinet Concerto, with the impressive New York clarinettist Michael Sussman. I immediately wanted to hear it again, both because I liked so much of it from moment to moment (the way the military mood of the first movement changes from Reveille to Taps; the enchanting slow waltz of the second movement, surrounded by ominous tremolos; the last movement’s eloquent passage for small string ensemble and the fading heartbeat at the conclusion) and also because I couldn’t figure out how all these episodes (or their influences — including Shostakovich and Virgil Thomson) held together. In Mozart’s concertos — or Carter’s — continuity is crucial. Here it was hard to detect any development. It’s almost an anti-continuum. But I want a second hearing to confirm, or contradict, my first impression. That may be the most important sign of a good piece.

SEIJI OZAWA completed his final Tanglewood season as director of the Boston Symphony Orchestra in a concert performance of Richard Strauss’s Salome, his notorious one-act opera, with Metropolitan Opera soprano Deborah Voigt making her first appearance in the title role. Voigt calls herself a " big girl, " so she sat out " The Dance of the Seven Veils " while Ozawa and the orchestra played it for all its lurid worth. In 2002, Ozawa will be leaving Boston to take over the Vienna State Opera, so the Viennese suspensions (was Salome doing a waltz?) weren’t inappropriate.

I didn’t attend the performance — I listened to the last scene, the climax of the opera, an apogee of operatic sensuality, on the radio. No problem hearing the singers over the huge orchestra. But Voigt was not only pouring it on, as she always does, usually rather abstractly. This time she had character in her voice. She was begging Herod for the head of John the Baptist. Importuning. Demanding. You could hear her demented though girlish insistence. And if in her first go at this role she didn’t have the profound sexuality of Ljuba Welitsch, the greatest interpreter of this role, she was a consistently living presence.

Ozawa conducted Salome in Boston a decade ago, with Hildegard Behrens. I found the orchestra " coarse without the saving grace of vulgarity " ; I also wrote that this " juggernaut of a performance lacked emotional undercurrents . . . Strauss’s underlying sense of the unspeakable. " So I didn’t particularly want to travel to Tanglewood to hear it again. But to my surprise, this time Ozawa seemed to follow Voigt’s every emotional turn. The playing — especially by the BSO’s new principal oboist John Ferillo (who comes to Boston from James Levine’s Metropolitan Opera Orchestra) — had a suppleness rare for Ozawa that I hope marks a new expressive plateau for the orchestra. It made me wish I had been there.