NORTHAMPTON — Blue Heron may have been founded as a Renaissance choir, but don't call the vocal ensemble that now.
"We were founded, it's true, as a choir — a choir to do Renaissance music — but as our understanding of performance practice in the past [has] evolved, and as we've learned more about the music and gotten more experience in it, a few things have emerged [to change that identity]," Blue Heron music director Scott Metcalfe said during a recent telephone interview in advance of the group's performance at Williams College's Chapin Hall on Monday night.
One of the changes is that the group doesn't necessarily sing all at once.
"Most music that we think of as choral music now from the 15th and 16th centuries was sung, normally, one person to a part," Metcalfe said, noting that there were occasional exceptions to that rule.
The director feels that many people view choirs as large groups blending their voices on every part with a conductor standing in front of them, leading them through sacred music. These perceptions are misguided, he said.
"All of those images are ways of thinking about vocal music that don't really apply to the music of the past and don't really apply to the music that we do either," he said.
Founded in 1999 and based in Cambridge, Blue Heron has received critical acclaim for its 15th and 16th century polyphony performances even as it struggles to shed the label of "choir."
"A continuing marvel of Boston's music scene, this superb choir has been making its way through the music of Johannes Ockeghem, the 15th-century Flemish composer," David Allen wrote for The New York Times in advance of a Blue Heron performance in October.
Metcalfe prefers a different description of the group. He likens Blue Heron to a chamber music ensemble — specifically, a string quartet.
"The vocal ensemble repertoire from the 15th and 16th centuries is much more analogous to ... the standard instrumental chamber music repertoire of our mainstream concert life," said Metcalfe, who is also a Baroque violinist. "There's a lot more in common between a madrigal by Cipriano de Rore and a string quartet by Beethoven. They're one-on-a-part pieces. They're extremely demanding. They're the highest form of music being composed at the time, so that's what we do. We're a chamber music group."
In Williamstown, six singers will focus on selections from de Rore's "I Madrigali a cinque voci" in a show titled, "Songs of Love and Death." The group is currently in the midst of performing and recording 20 madrigals, or poems that can be set to music, from the book. The core of this work is 16 sonnets, many of which are authored by Francesco Petrarch. At Williams, Blue Heron will present no more than 10 of the madrigals. They're each in five parts.
"They're quite sober," Metcalfe said. "They're incredibly absorbing, and we're just going to have to see how many it seems like is the right amount to present in a concert."
Even though the music is centuries old, it has rarely been explored.
"Most of the repertoire that we do, none of us has ever heard before," Metcalfe said. "A lot of it's not been performed. A lot of it's never been recorded."
In that sense, Blue Heron doesn't feel like an early music ensemble. In some ways, it's the opposite.
"We're always digging for new material, so we do sometimes feel like a new music group," he said.
Jessie Ann Owens, a professor at University of California, Davis, introduced Blue Heron to the de Rore book. According to Metcalfe, Owens told Blue Heron she thought only two or three of the madrigals that had been recorded. Subsequently, Owens and Blue Heron received a grant (the American Musicological Society's The Noah Greenberg Award) to begin working on further preserving the Franco-Flemish composer's work. Metcalfe believes de Rore's music will grab a contemporary audience.
"It will be all music that no one's ever heard before. It's very inviting music and very rich and complicated ... to see how Rore is responding to [the poetry] and putting together pieces into their own cycle ... [is] very, very interesting," he said.
"These are really what people think of when they hear the word, 'madrigal,'" said Jason McStoots, a Blue Heron tenor who will sing in Williamstown.
McStoots, who has been a member of the ensemble since 2005, echoed Metcalfe's assessment of the group's identity.
"We really approach it as if we [are] soloists, not as if we are a choir," McStoots said, "and I think that is relatively groundbreaking for this music. We hear so many people talk about this as choral music, as using words like blend, and the idea being that it's sort of a homogeneous mix. And Scott doesn't think like that all, and neither do the rest of us. It's really four or five or six solo performers each fulfilling the ideal role as best they can."
Benjamin Cassidy can be reached at firstname.lastname@example.org, at @bybencassidy on Twitter and 413-496-6251.