IN THE DEEP HEART’S CORE: A MYSTIC CABARET, Bailiwick Repertory. William Butler Yeats fused the roughness of folklore with literary refinement in his search for “the deep heart’s core” of himself and the Irish people, and composer Joseph Daniel Sobol does the same in this rich, sometimes ravishingly beautiful music-theater piece based on Yeats’s brilliant poems and essays. A two-act program of sung and spoken texts sheds lights on Yeats as artist, politician, theatrical producer, unrequited lover, and apocalyptic visionary, and captures the complexity of the man who rightly asserted, “We make out of the quarrel with others, rhetoric; but of the quarrel with ourselves, poetry.”

Staged with satisfying simplicity by David Zak, this lovely production features folksinger Kathy Cowan, who combines a vibrant, poignant soprano with a radiant, openhearted presence; she’s given able support by the fine baritone Tom Orf and tenor-guitarist Sobol in an array of solo and ensemble numbers, including several folk-dance segments. The dynamic fiddler Andrew Bird leads the Kiltartan Road Ensemble in Sobol’s music, which is based in a folkish string-band idiom but reveals the composer’s craftsmanship in offbeat nuances of melody, harmony, and rhythm. Lori Willis’s rustic backdrop painting, Jonathan Parsons’s subtle lighting, and Michael Alan Stein’s turn-of-the-century costumes evoke a sepia memory of rural Ireland, complementing the themes of heroic action and anguished reflection that inform Yeats’s tales of dead rebels, passionate women, mischievous fairies, and occult revelations.