Monadnock Music recently treated us to Elliott Carter’s largest orchestral work, his hour-long musical odyssey, Symphonia. Last week we got one of his smallest, called Shard — two and a half minutes for solo guitar. The performer was Carter’s favorite guitarist, David Starobin, for whom more than 300 works of contemporary music have been composed. Shard, in Starobin’s concert for the Longy School’s Showcase Series, was the most demanding and intricate piece he played in a delightful (and delightfully brief) evening that also included a special guest accompanist, septuagenarian composer George Crumb.

Starobin played a glamorous black-lacquered cutaway, but there was nothing fancy or pretentious about him. He talked uncondescendingly to the audience, explaining changes in the program and filling us in on some musical history. The first half was music for classical guitar. Fernando Sor, for Starobin the greatest of the 19th-century guitar composers, was also the most cosmopolitan (he supported Napoleon and fled Spain after Napoleon was ousted, then lived in Paris, London, and St. Petersburg). Starobin offered a lilting Minuet, a melancholy "Lesson," two Études, an Andante, and a galloping Galop with refined understatement, with an infallible ear for phrases, convincing melodic and rhythmic shapes, and musical line. There were also charming sets by Giulio Regondi, including a piece originally composed for the concertina (Regondi, Starobin said, was the "concertina king"), and Beethoven’s friend Mauro Giuliani (principal cellist in the world premiere of Beethoven’s Seventh Symphony), the last of whose Nine Fantasy Pieces, a tiny lament with a sad ending, was the most touching work in the first half.

One theme of the evening was dance music. Starobin has been commissioning short dance pieces, and he played a handful of them after intermission: William Bland’s True and Authentic Gymnopédie (an homage to Satie), David Liptak’s hypnotically repressed Forlane, and Bryan Johnson’s zippy Think Fast (all composed since 1998). One piece I couldn’t help being curious about — it was listed but not played — was Du<t-75>ˇ<t$>san Bogdanovi<t-75>´<t$>c’s Psychic Engines, from 1997, and written, if the birthdate in the program is to be believed, when the composer was two years old!

The "major" work was George Crumb’s response to Starobin’s invitation — which turned out to be an entire suite rather than a single short piece, and not a sequence of dances but a series of musical portraits of the Crumb family dachshunds: Mundus Canis, 5 Humoresques for guitar and percussion (1998). For each of these impressionistic sound bites, Crumb himself shook or hit or scraped a different percussion instrument. Maracas accompanied Starobin’s bent guitar notes for the elegant Tammy. "Furioso" Fritzi got Crumb’s hand-held drum and some guitar tapping from Starobin. "Languido" Heidel had Crumb, with soft mallets and a wire brush, striking gongs (one a water gong) and upstaging Starobin entirely. Emma-Jean ("coquettish" and "grazioso") was an exotic hootch dance, with sticks and hushed cymbal. And Yoda had not only a clicker and a güiro (scraper) but also vocals: "Yoda! Yoda! Yoda!", Crumb repeated, before the final "Bad dog!"

This was cute and silly, Crumb at his softest edge (which is pretty soft), sonically sophisticated but musically thin, especially compared to Carter’s little Shard (1977), which had more music in its two and half dazzling, brilliantly condensed minutes than all the rest of the pieces put together. Employing a variety of guitar strokes (picking, plucking, strumming) but no gimmicky gestures, it moves through a whole sonata’s worth of experience, from fanfare through lyric introspection to energized scherzo to a poignant, glinting coda dissolving as it ascends into the æther.

You can hear Starobin play Shard on volume four of The Music of Elliott Carter (Bridge Records — the label devoted to contemporary music and historic performances that Starobin founded), and then hear how Carter placed it inside a fascinating longer piece called Luimen (archaic Dutch for "whimsical moods"), which combines delicate plucked instruments (guitar, harp, mandolin) with heavy brasses (trumpet and trombone). But this is such a rich, demanding work, it was breathtaking to see Starobin nail it in person.

AFTER LAST WEEK’S BSO BILL of Mozart and Bruckner, Bernard Haitink was back leading two of Mozart’s late masterworks, the G-minor Symphony No. 40 and the Requiem — the latter, since Amadeus, Mozart’s most popular piece of music. Symphony Hall was packed. The G-minor had no surprises. It worked because it was so beautifully played, in spite of (or because of?) the emotional abstraction, the square phrasing (imagine . . . someone . . . speaking . . . one . . . word . . . at . . . a . . . time . . . giving . . . each . . . word . . . equal . . . emphasis), and the relentlessly moderate tempos (the up-tempo Andante sounded more like music for the Sugar Plum Fairy than a profound Mozartian utterance).

The Requiem was dedicated to the memory of a dear friend of Haitink and his wife, Lynette Lithgow, a fellow at the Kennedy School, who was killed in her native Trinidad last December. This was a full-bodied, blessedly old-fashioned, and noble performance in which Haitink actually let himself express passion. He was positively trembling with intensity during the Dies Irae, though the essential mysteriousness of the Requiem eluded him. The Tanglewood Festival Chorus responded with force, though at the cost of some precision. The strings were particularly glowing. Trombonist Norman Bolter rather smeared his difficult solo in the Tuba mirum.

The excellent vocal quartet had one surprise. Replacing soprano Christine Schäfer, ill with the flu, was one of Boston’s pre-eminent Mozart singers, Kendra Colton, an Emmanuel Music regular whose shining voice soared above the Boston Lyric Opera’s otherwise negligible production of Il re pastore five years ago. The soprano has the Requiem’s first solo line, and Colton’s entrance gave one heart. She capped the string of solos in the Tuba mirum, and near the end, she was the radiant embodiment of the everlasting light of the Lux aeterna. Two of her partners were also making their BSO debuts: plum-voiced mezzo-soprano Sara Mingardo (who appears on the Claudio Abbado Requiem with Karita Mattila and Bryn Terfel) and light-toned Met tenor Richard Croft (who sings on Boston Baroque’s Requiem recording); bass-baritone John Relyea, a student of the legendary Jerome Hines, was returning after his BSO debut in Mozart’s C-minor Mass under Seiji Ozawa at Tanglewood three summers ago. We’ve heard worse.

JANUS 21 has a more appropriate name than ever. The chamber group, named after the two-faced demigod who looks both forward and back, is itself looking forward, under the new directorship of pianist Max Levinson and violinist Andrew Kohji Taylor, but the performers who gave the group its identity over the past decade, mezzo-soprano Jane Struss and tenor Michael Calmès, are still sharing the bill. Last summer’s concert was something of a hash. But their latest outing, at Longy, under the slightly misleading rubric "Russian Jewels" (there was little glitter or glamor in this ambitious and often grim program), was both more coherent and more consistently effective.

It started with a good idea: six Rachmaninov songs (among his most eloquent) about nature, including settings of poems by Pushkin and Tolstoy. But Calmès, who can be a refined artist, pushed his voice to painful volume levels that made it both unsteady (even in falsetto) and out of tune, exchanging nuance for rhetoric. That was also true of pianist Timothy Bozarth’s accompaniment — though he seemed more engaged when exploring the more contemporary challenges of Alfred Schnittke’s 1978 Cello Sonata No. 1, with the exciting young cellist from Vladivostok Alexei Romanenko. In the slow last movement, the eerie piano scales over rising and falling cello pizzicatos gave me goosebumps. And how often do chamber groups schedule music by Russia’s late postmodernist master?

The second part of the program was more satisfying. Struss embodied every nuance of Prokofiev’s intricately woven Five Poems of Anna Akhmatova, and pianist Brian Moll, a long-time partner of Struss’s, showed how much the piano could wrap itself around the singing. Prokofiev also lived up to the challenge of setting these extraordinary poems, which are so personal and yet so representative of Russian attitudes:

Willows spread across the empty sky

Weeping transparent branches.

Maybe it is better that I do not become your wife.

The highest of the evening’s high points was the stunning performance of Shostakovich’s 1944 E-minor Piano Trio, with Janus’s youthful new directors, Levinson and Taylor, joined by Romanenko. This masterpiece is a miracle of concision, with its elegiac opening movement (beginning with a lonely cello in high harmonics sounding like a weeping violin — or a violin trying not to weep) and a piano singing a haunting song (Levinson at his most soulful) while the two other players tap their strings with their bows. A high-spirited second-movement dance (Taylor, so velvety in the previous Andante, was not afraid to sound like a scratchy country fiddler) precedes a doom-laden Largo. The macabre Finale is chilling, skeletal vaudeville (the Jewish theme — a little klezmer, a little Weill — suggests that Shostakovich might have been thinking of the concentration camps), with an irresistible beat and an unforgettable tune; it’s interrupted by a reminiscence of a luminous Eden before the final, inexorable death march.

Not only did these young players (average age — at most — 27?) catch the wildness, the satire, and the dire pain, they also captured the music. I was reminded of the glorious days when Yo-Yo Ma, Lynn Chang, and their Harvard classmate (pre-med) Richard Kogan played trios together. This happy configuration suggests that Janus knows exactly which direction to face.