A vigorous performance of the "Brandenburg" Concertos or The Messiah will always draw a crowd -- the high Baroque, blockbuster era of Bach and Handel still reigns in the world of classical music. But so-called "early music," from the centuries prior, is now burgeoning in popularity. Call it a renaissance.

The older music appeals, ironically, because of its freshness. Not to mention exoticism and clarity. It uses fewer instruments -- often ones slightly strange to the modern ear -- or relies entirely on the human voice. One of the joys of an early-music concert is the chance to hear rarely performed pieces and composers. The University of Vermont's Lane Series has made early music a staple of its programming, and this week has a doubleheader: the Blue Heron Renaissance Choir on Thursday and Baroque instrumentalists Ensemble Caprice on Friday.

Among the plethora of early-music groups touring today, few are professional vocal ensembles; Blue Heron is one of just a handful in North America dedicated to performing choral music from the Renaissance period. Scott Metcalfe is Blue Heron's director. If his name sounds familiar, it's because he was born and bred in Burlington, and is the son of a local musical power couple -- conductor William and harpsichordist Elizabeth Metcalfe.

Anyone who has heard of the composers on Blue Heron's program this week may be ready to challenge Ken Jennings' 75-game winning streak on "Jeopardy." Works by obscure Englishmen Hugh Aston and Robert Jones make up "A Mass in Canterbury c. 1540." The pieces come from the Peterhouse partbooks -- a set of long-forgotten manuscripts containing nearly 50 pieces that exist in no other source material.

"It's hard to get your head around how much great music there is from the 16th century," says Metcalfe, "and most of it none of us hears." Indeed, Renais-sance Europe was a hotbed of composing. Royals used music as a symbol of their power as well as for entertainment. And with music integral to all aspects of worship, the church was a veritable MTV of its day: the most influential patron, dictating styles, and launching careers.

Metcalfe tells a fascinating story of how intricate, five-part Latin vocal pieces, such as those in the Peterhouse collection, became politically and artistically radioactive. The tale is bound up in Henry VIII's beef with the Catholic Church: When the Pope denied the randy but heirless monarch a quickie divorce, Henry founded his own national church.

The English Reformation dictated an extreme makeover in religious music. Anything associated with Catholicism was rejected, including stylistic choices in musical composition such as polyphony (multiple intertwined melodic lines) and melismas (long flowery vocal runs on a single syllable). Some composers, such as Thomas Tallis, radically changed their tunes to suit the new political mandate. "He had to make a living," says Metcalfe. "They all worked for the church."

Others, like Aston and Jones, fell into obscurity, their works shelved or destroyed. Each voice part of the Peterhouse manuscripts was written out separately, and as they "wound from here to there and through various private collections," Metcalfe notes, "somewhere along the way one of the five partbooks went missing." With the help of an English musicologist who has reconstructed the missing tenor book, Blue Heron is able to perform "new" music that is nearly half a millennium old.

Metcalfe is a newly minted musicologist himself, having just completed a Master's at Harvard in historical performance practice. For a choral group, he says, this means looking at issues such as "voice types, pronunciation, choral forces, how many singers on how many parts and what pitch, exactly, might things have been sung at."

While these concerns may sound academic or arcane, Metcalfe good-naturedly insists that focusing on how the music actually sounded helps get at the core of what makes it "emotionally engaging and moving." In a phone interview from his home near Cambridge, Massachusetts, Metcalfe discusses his group's upcoming concert -- featuring "rapturously beautiful" music that was almost lost to history.

SEVEN DAYS: Why should the casual concertgoer care whether a choir is faithful to details of historical performance?

SCOTT METCALFE: Oh, I don't think it matters in the least. I think that this is just fantastic music, and I resist very strongly any idea that people ought to come to concerts like this because it's primarily of historical interest or because there's something sort of esoteric about it, or that you have to be interested in odd things historically in order to find this music beautiful. That to me is absurd.

SD: If the music is going to sound pretty no matter how the Latin is pronounced, then why be faithful to the original?

SM: The question for me is, 'How do you get into a relationship with the music that allows its power to come through the most clearly?' And for me that comes through knowing as much specific about the performance style as we can know and trying that out . . . so that the way you perform a piece of 16th-century English music doesn't make the same assumptions that you would make to sing a piece of Bach or Stravinsky. We have a lot of choices about what kind of sounds we make. And we don't want to limit our palette in any way. But we want to find out what specific colors and types of interpretation make the music most alive.

SD: Aren't the challenges greater with vocal music than with instrumental pieces? How do you know what a voice sounded like four or five hundred years ago?

SM: With voices we have no way of knowing . . . I think we can assume that the basic human organism has not changed that much. People have done work about people's heights and nutrition and the age at which men's voices matured and changed, and length of the larynx -- and I have to say the evidence for all that stuff is somewhat equivocal.

SD: Some of the great old cathedrals are still around, and we know about their acoustics.

SM: We have some information about the sonic spaces that they were in, although, again, that may have changed because they may have had tapestries up on the wall. It's not exactly the same, but we do have some idea about sound. In the case of the music that we're doing this week, we do know something about certain specific choral establishments around the 1530s in England.

SD: Like schools?

SM: Choral foundations, attached to churches. We know at least who was on staff. It's very hard to get from there to who actually sang a polyphonic mass on Sunday morning. Just because there were 12 singers on the payroll doesn't mean that they all sang every day.

SD: It sounds like there are a lot of puzzle pieces to assemble.

SM: The further you go back, the harder it is to know anything specific. It's pretty safe to say that in England, at the beginning of the 16th century, at the larger cathedrals -- the kind of place where this mass that we're doing would have been sung -- the choirs average 12 to 15. There are usually two or maybe three people on a part, generally more on the top part, and those would have been boys.

SD: During the English Reformation, were a lot of music manuscripts lost or destroyed with Henry VIII's confiscation of the monasteries?

SM: I think it inevitably must have been so, because there was all this music that was suddenly completely useless to them. Actually, the music that we're doing on this program is part of this story. The Peterhouse partbooks are copied probably in 1540 for Canterbury Cathedral, just as it was being refounded as a secular institution. It had been dissolved as a monastic cathedral. There was this moment where they needed all this new music for this new foundation. And so this guy, probably from Oxford, sits down over the course of a whole summer and copies about 75 pieces into partbooks. And they're these huge, late-Medieval settings of the Mass and of motets -- it's this last real outpouring of incredibly florid and melismatic English polyphony . . .

Both the Mass and the Hugh Aston motet that we're doing on this program are of that style . . . They're amazing: You'll get the beginning of a phrase, quite clearly set out, and then suddenly everyone's just off on "oh" or "oo" or "ee" and it's for a page of melisma! So this guy copies these five books, gets them all together, sends them off to Canterbury, and the next thing you know, they've suddenly declared that all of this stuff -- you can't sing it anymore.

SD: It's music, but because it was somehow Catholic music, it's like "Catholic -- bad! We need new music."

SM: Exactly. There's a complete change in the musical style required for music they're going to sing in church. They want it to be in English. They want the words to be clearly understood, so they want it to be basically syllabic. They don't want all this elaborate polyphony. There's this idea suddenly that austerity is more pious, and there's this suspicion of this incredibly sensuous kind of writing that's been going on up to this point, as if that's somehow not divine, but that's worldly and that's going to trap people into occupation with sensual things on Earth . . . So it's the end -- suddenly all of this repertoire is completely obsolete. And it was never used after that point.

SD: What is it about early music that resonates with modern audiences?

SM: I hope people go to concerts because they find the music moving -- that's certainly what we're after. That's what I would aspire to as a group, to get people in their guts and communicate some of the real emotional directness of the music that we're singing. Singing especially gets to someone's heart more directly than any other kind of music because it's the voice, it's us, it's the direct speech of a human being.