Fairy tales in Merola’s ‘Transformations’ by turns edgy, thin

Even before Stephen Sondheim and James Lapine (with an assist from the psychologist Bruno Bettelheim) laid bare the psychological currents underlying traditional fairy tales with “Into the Woods,” the poet Anne Sexton had put her own knowing gloss on the Brothers Grimm. “Transformations,” her 1971 collection of poetic retellings of these stories, underscored their dark strains of madness and incest, as well as mildly comical highlights referencing Thorazine and midcentury American life.

Then the material became transformed once again into composer Conrad Susa’s chamber opera, which got a suitably shadowy production on Thursday night, July 21, from the young artists of the Merola Opera Program. By this time, the number of subterranean streams running through the familiar adventures of Snow White, Rapunzel and the rest can become daunting.

Yet the striking thing about “Transformations” — and surely one of the reasons the piece has become such an American staple, especially on college campuses and in training programs like Merola — is how lightly it all goes by. The 10 scenes offer gentle tweaks of the source material, hinting at the undercurrents without always delving into them very deeply.

The ensemble of eight singers move fluidly among various dramatic functions, serving alternately as story characters, narrators, commentators and interpreters. Susa’s music, scored for a taut, jazzy little ensemble of instruments, tips its hat repeatedly in the direction of Kurt Weill, and the popular strains — buoyant but acerbic tangos, ballads, mambos and so forth — coexist peaceably with extended, sometimes jittery stretches of recitative.

The result is by turns invigorating and slightly threadbare, a series of interpretive dispatches that are now a bit past their sell-by date. Even if “Into the Woods” had not raised the bar so prohibitively on this sort of project, the very breeziness that makes much of “Transformations” so engaging in performance also leaves a sense that there are things being left unsaid.

The Merola production, at least, doesn’t shy away from the work’s darker edges. The score calls for a setting in a mental institution, but when Merola last staged the piece a decade ago, it played out in a garishly bright-hued suburban lawn.

This time, director Roy Rallo and scenic designer Marsha Ginsberg, working deftly with the tiny stage at the San Francisco Conservatory of Music, have unapologetically set the action in an externalized vision of the unconscious. Act 1 is littered with a few disconnected but iconic props — sideboard, sofa, bean-bag chair — while Act 2 unfolds in a dark cave. Salvador Dalí’s dream sequence for the Hitchcock classic “Spellbound” comes often to mind.

Under conductor Neal Goren’s crisp musical leadership, the eight Merola singers ran through their elaborate tag-team assignments with unruffled ease and often plenty of vocal glamour. Soprano Teresa Castillo was a particular standout, bringing power and florid elegance to a range of roles that included Rapunzel and Gretel, and tenor Boris Van Druff made robust, heroic contributions throughout.

There was even a little surprise drama at the midpoint, as soprano Shannon Jennings — who had soldiered bravely and often alluringly through Act 1 in the face of some vocal troubles brought on by illness — gave up the struggle in Act 2. Her colleague Mary Evelyn Hangley came to the rescue, giving a vibrant vocal performance from the pit while Jennings mouthed the music from onstage.

Matthew Anchel’s hefty bass and the elegant low register of soprano Chelsey Geeting made a persuasive pair, and there were strong showings too from baritone Andrew G. Manea and tenors Brian Michael Moore and Isaac Frishman. These fairy tales have not always been told, or sung, so appealingly.

Transformations: 2 p.m. Saturday, July 23. $45-$65. San Francisco Conservatory of Music, 50 Oak St., S.F. (415) 864-3330. www.sfopera.com