WINTERREISE: Thomas Quasthoff and James Levine were in their element.

One sign of Boston’s rich classical-music scene is that there are often hard choices to make when two outstanding events are scheduled at the same time. I can’t remember a worse conflict than the one at 3 pm last Sunday. At Symphony Hall, James Levine was accompanying bass-baritone Thomas Quasthoff, one of the world’s greatest living lieder singers, in the greatest song cycle ever written, Schubert’s Winterreise (“Winter Journey”). At Jordan Hall, Donald Teeters was celebrating his 40th anniversary leading the Boston Cecilia, which must have played more Handel operas than any other group in town, with a spectacular line-up of veteran and up-and-coming Handel singers in the Handel bash to end all Handel bashes — an endless stream of some of the most gorgeous arias and choruses ever written. Impossible. Since Winterreise is shorter, I opted to hear it whole then rush across the street to Cecilia. I wasn’t disappointed by either one.

One of countless extraordinary moments comes in the second song of Winterreise, “Die Wetterfahne” (“The Weathervane”). “Inside, the wind plays with hearts,” the singer laments over the faithlessness of his beloved, “just as it does on the roof — only not so loud.” Quasthoff and Levine took a long pause and Quasthoff sang the last part, “nur nicht so laut,” almost in a whisper, as if in awe of the mystery of the human heart and its ruthless, unpredictable changeability. I’ve seldom heard performers make so much of this moment. But it was not a gimmick. It felt completely natural and lived through. Even in cavernous Symphony Hall, I was drawn into one of music’s most intimate experiences.

Quasthoff was in his element. His voice has deepened and darkened, and his beautiful tone filled out every phrase, loud and soft, high and, especially, low. Levine gave one of his most sensitive, understated, eloquent performances. They made particularly striking the several songs in which there are abrupt switches between a twinkling fantasy of hope (a dream of springtime, the arrival of a letter) and the stark, hopeless actuality. The loud explosions after Quasthoff’s held-back, trancelike singing always sounded like escaping cries of woe.

In this late work, Schubert explores questions of existence: of God and pain. “Mut!” (“Courage!”) is a hearty drinking song that ends, “If there is no God on earth,/Then we ourselves are gods.” But this is not the answer to the question “Why, if I have done no wrong,/Should I shun mankind?” Quasthoff sounded almost hypnotized by the “signpost” that pointed him on his endless journey from which no one returns, just as he seemed mesmerized by his vision of crows ceaselessly circling him.

The last song, “Der Leiermann,” is the most poignant and the most profound. The singer meets an old organ grinder, barefoot, playing his hurdy-gurdy beyond the village, his tray empty of coins, his only audience snarling dogs. Quasthoff pleaded to go with the old man, to have him turn his suffering into the organ grinder’s songs. What else can one do with suffering except turn it into art? The cycle is devastating. The performance was quietly devastating. Yet in its beauty and inwardness and human understanding, also exalting.

At the Cecilia, I arrived just as mezzo-soprano Pamela Dellal was launching into Handel’s great lament from Rinaldo, “Cara sposa” (“Dear wife”), in which the hero desperately searches for his lost wife. Dellal’s voice was ripe with warmth, yet she could also handle the difficult runs. Then soprano Karol Bennett, absent from Boston too long, answered with Almirena’s lament, the aching “Lascia ch’io pianga” (“Let me weep”), and her lavish embellishments intensified the impression of her weeping. Tenor William Hite combined power and agility in a scene from Joseph and His Brethren, and soprano Sharon Baker tossed off brilliant roulades in her aria prophesying victory. Tenor Aaron Sheehan sang Jephtha’s great prayer for the daughter he is about to sacrifice, “Waft her, angels, through the skies,” and Jeffrey Gall, in his last public appearance as a countertenor before he becomes a full-time baritone, sang Cyrus’s heroic defiance of “Destructive war.” Teeters and the chorus closed with the magnificent hymn to Solomon, “From the censor curling rise.”

After the performance, I heard people raving about soprano Nancy Armstrong’s brilliant aria from Semele (she knocked me out when she sang this with Teeters in 1981) and William Hite’s tender “Where’er you walk” (also Semele), the much-missed baritone David Arnold and the happily present Robert Honeysucker, mezzo-soprano Krista River’s Sheba, soprano Jennifer Cooper’s Cleopatra, tenor Charles Blandy’s Judas Maccabæus, and the chorus’s rousing “See, the conquering hero comes” and sublime “Nightingale Chorus” from Solomon. Teeters was the hero. I wish I could have been there for the entire concert.

Levine returned to the BSO for the first time this year with a beautifully proportioned program of smaller orchestral pieces. He started with Mozart’s irresistible Symphony No. 29, in A (K.201), which he led with an urgency that made it sound in the first movement like a harbinger of Don Giovanni, and in the second like an early version of the ironic seduction duet between Guglielmo and Dorabella in Cosí fan tutte. He closed with a tender performance of Brahms’s Serenade No. 2, also in A — a piece without violins, but with the violas adding warmth to the glowing winds.