Capella Clausura is nothing if not ambitious. Elena Ruehr (composer) and Gretchen Henderson (poet/librettist) wrote their Cassandra in the Temples, (described variously as a poetic opera and a choral opera) for performance by the hip New York-based vocal ensemble Room Full of Teeth. The “Teeth” premiered it at M.I.T. almost exactly a year ago. While Capella Clausura’s Director Amelia LeClair did not hear that performance, she did hear Ruehr’s Eve, performed by The Cantata Singers BMInt review here]. That powerful experience moved LeClair to approach Ruehr about a work for Capella Clausura. Ruehr seized the opportunity to suggest another performance of Cassandra, this one with staging so that the opera could be performed with the multiplicity of media that defines the genre.

CC will also feature Aaron Copland and Rebecca Clarke works at Lindsay Chapel in Boston’s Back Bay on Saturday night, and at Eliot Church in Newton on Sunday afternoon. Information here.

I couldn’t think of any operas that are comparable to Cassandra as I sat in on a rehearsal last Saturday. The poetry is sometimes ethereal and abstract, often profound, but without much of a conventional narrative. But there is a drive and energy to the work, at times powered by the intricacy of the musical language and at other times by its simplicity. Despite a sound-palette rich with dissonance, the overall framework is tonal, and passages of octave singing or unisons anchor the music and add a memorable quality. Henderson’s libretto itself, with its visual aspects of poésie concrète, already offers a multi-media experience (the audience will receive a full libretto in their program). The music adds further artistic dimensions, and with the staging (by DeAnna Pellechia) and costumes (by Cheryl Hayden), the result is sure to be a thought-provoking and richly layered experience.

Take one example near the end of the opera: the chorus “Sing We Home.” Henderson (in her preface, she compares it to yogic, meditative chanting practices) spins the phrase in a spiral and Ruehr’s music does the same, creating a twisting column of overlapping and precisely interlocking motives. It suggests (perhaps) an elaborate ornate Greek column, or an abracadabra-esque incantation, evoking magical charms, blessing the journey.

While sometimes (as in “Sing We Home”) the music is architectural in structure, other passages are a more transparent. Also the layering of meanings evokes (and perhaps draws from) many ancient (or at least very old) musical techniques, resonating from 13^th century motet, conductus, etc. Another antique resonance is heard in a sinuous solo vocal line (sung by Cassandra) with rich ornamentation, slides and inflection, like some exotic middle-eastern chanting or plaintive some.   This melody drifts over a backdrop of floating drones.

LeClair has assembled a brilliant and charismatic group of singers, featuring Adriana Repetto as Cassandra. Repetto’s voice is luscious, full, and warm, while Eric Perry (as Apollo) has more of the clarity of an early music singer, although replete with dramatic power and intensity.

Cassandra offers layers of meanings, and many possible metaphorical interpretations – one of which is the environmental lesson. Are those who refuse to listen to the Cassandras of climate change going to sway until Troy/civilization is destroyed? In a week when the President announced rejecting plans to build the Keystone XL Pipeline (although large sections of the pipeline are already completed and in use), and investigations were launched into Exxon Mobil having lied about the dangers of climate change, that interpretation has a timely impact.

Choral works drawing on themes of Greek antiquity—including Byzantine chants by the 9^th-century abbess Kassia, and Rebecca Clarke’s soaring and transcendent “Chorus from Shelly’s Hellas” for five-part women’s chorus will also be featured on the thematically consistent program. One of my favorite works by Clarke, it’s also one of her many works un-performed in her lifetime, and we are not even sure when or why she wrote it. Two early works by Aaron Copland invoking antiquity through their settings of biblical texts will compete the concerts.