"It's just so Nordic," he says, "icy and cool, clear and crystal."
Esenvalds' Stars uses Tibetan singing bowls and tuned water glasses which, Rosser explains, catch the shimmering sound that, all those centuries ago, people imagined the music of spheres might be like.
"The effect of those ringing glass tones alongside voices is just stunning," he adds. "It's a cosmic tone poem."
Rosser is pleased to include music by the 73-year-old Morten Lauridsen, whom he describes as the father of almost all modern American choral composition and the inspiration behind Eric Whitacre, "the world's choral rock star".
"Lauridsen doesn't write those easy, jazz-inspired pieces that end up being a bit empty, making pretty pictures that don't go anywhere," he points out. "His wonderful feeling for the texts being sung gives his music a dramatic purpose and takes you on a decent musical ride."
Next Sunday's musical journey includes two works by Auckland's David Hamilton. Rosser feels a long-standing commitment to this composer, saying he has written consistently high-quality choral music. He likens one of the pieces to "those Japanese watercolours so popular in the 1970s; they have that same diaphanous feel when you're singing it."
Transcriptions from the light side bring some breezier takes on these galactic orbs, he says, laughing, with a Ward Swingle arrangement of Debussy's Clair de Lune and Stateside standards such as Fly Me to the Moon.
The challenge here is the constant problem of "a choir looking and sounding geeky".
"We have to up our twang level," Rosser says, with a smile. "You have to use what classical singers would call a squillo voice, where vowels are lifted and not so deep, making you sound jazzier without losing quality."
Viva Voce has been entertaining its audiences for 32 years, its presentations punctuated by Rosser's characteristically urbane commentaries. The intimate scale and clear acoustics of the concert chamber suit them well and, although a church may notch up the choral resonance, "pews are a little restrictive and give the audiences a message that we don't want".
For Rosser, it's important we get up from our computers and experience music in 3D.
"It's easy to be locked in front of a filmed performance that's been edited and engineered to death, meaning that you lose that thrill of live performance," he stresses. "I want to see human beings in front of me, using skills and taking risks. That's what I love about live performance."
