Comes in all sizes

For all his oft-proclaimed eternal appeal, J.S. Bach has been subject, in recent years, to an awful lot of fad diets that have drastically altered his music's size, sound, silhouette and weight.

With performing forces ranging from lone vocal soloists to choral armies, the Mass in B minor has never arrived in so many different guises in such prominent places. From the Netherlands Bach Society to the Bach Choir of Bethlehem, the music could sound like a particularly mighty madrigal or the collective voice of a nation.

It's all good. Though the work has never lacked admirers, it frightens off substantial interpreters. Not so much composed as assembled and adapted from past works (and for no specific occasion), the Mass in B minor is far too gargantuan to fit any liturgical niche or genre; it has no descendants and only distant antecedents. Conductors from Arturo Toscanini to Wolfgang Sawallisch admired it on their knees but couldn't devise a performance strategy. Even the Bach-savvy Otto Klemperer abandoned a recording of the piece in midstream when he started disagreeing with his own views.

Options, lots of them, can only enhance the piece's public life, and that makes sense for the 21st century. In Bach's time, music was confined mostly to churches and coffeehouses; in our time, Bach is heard in all sorts of places.

In fact, the best explanation for the big-Bach approach heard annually at the Bethlehem Bach Festival (which ended yesterday) isn't that it's some living anachronism from Victorian times, maintained by provincial isolation and slavish tradition. The festival's identity lies as much in the churches where the music is performed as it does in the groups that perform it. And at one point in the opening weekend's Mass in B minor, the 150-voice chorus was scaled down to a chamber-sized group. But in the Packer Memorial Church acoustic (which gives a good, well-defined sound to large choruses because it lacks the long reverberation of grander churches) that passage made only a ghostly impression. Without big Bach, the festival wouldn't have the communal, big-audience experience that has made it famous.

The Netherlands Bach Society - heard last month at the Metropolitan Museum of Art's Grace Rainey Rogers Auditorium and in its excellent new recording of the Mass in B minor on Channel Classics - represents the far opposite stance: Aligning himself with Joshua Rifkin's long-derided 1982 recording that had one voice to a part, conductor Jos van Veldhoven has become convinced of the approach's historic validity. He has five singers handling arias and choruses, plus periodic participation from a 10-voice ripieno contingent. One advantage of solo voices is a specificity of expression not possible with choruses. Given the music's wealth of detail, this is good - in a modern auditorium where details can be heard.

The middle ground is represented by the Bach in Notre-Dame de Paris DVD on Virgin Classics, with the Ensemble Orchestral de Paris and an all-star lineup of nonspecialist soloists (Joyce DiDonato, Dietrich Henschel) conducted by John Nelson. In a space like Notre Dame, maximum lung power would seem necessary. Maybe not. In this live recording of the Mass in B minor, the 38-voice Maitrise Notre-Dame de Paris projects itself with an electricity born of conviction - the strength-in-numbers force of a chorus combined with individual sense of responsibility to pull one's expressive weight at all times.

And do they ever. Their power is apparent in the sound decay resonating through the cathedral after the music stops. Once past some early phrasing eccentricities, the performance develops to one of the best ever, with a single odd reservation. The accelerator-to-the-floor "Cum Sancto Spiritu," which probably has historical accuracy in its favor, becomes an eye-crossing instance of virtuoso choral singing. But with so many notes bouncing around so fast in that church acoustic, a newcomer to this music might find this passage almost unintelligible.

When practicality plays havoc with historical accuracy, the healthiest way to use musicological research is as quality-control insurance. Bethlehem makes big Bach work because the singers know what they're up against when creating a wall of sound, and conductor Greg Funfgeld molds it with any number of articulation solutions to big-Bach balance problems.

Compare this with the bad old days - the 1970s - when the idolized Herbert von Karajan recorded the Mass in B minor with his gleaming Berlin Philharmonic Orchestra in the foreground, and, as digital remasterings have revealed, the famous Wiener Singverein trailing along in amazingly ragged form. Even if the stilted performance didn't sound like Bach on Thorazine, perhaps only 60 percent of what the composer wrote could find its way through the sonic soup to your ears.

In light of that, the famous academic firestorm that greeted Rifkin's one-voice-to-a-part approach was irrelevant: As someone who first learned this music as a chorister rather than as a listener, I found Rifkin to be the first to make me hear the Mass truly without having to sing it.

His stance also happens to be in step with our brevity-craving times, particularly since the Dutch recording finds ways to project things that previously seemed to require expanse. The trudging-to-Golgotha tragedy that infuses Sergiu Celibidache's conventional-instrument 1990 EMI recording of the opening "Kyrie" requires 14:41 minutes. The Dutch project similar doom in 10:35 - and go deeper and darker with the later "Qui tollis" by projecting an illusion of agonizing slowness. And for those who believe smaller forces automatically dictate faster speeds, the 1998 big-Bach Bethlehem recording of the "Kyrie" is a minute faster than the scaled-down Dutch.

So nobody is right or wrong. Some performances are more right than others - at different times and places. Rules are elastic. The point is to have a personal and compelling vision of the music that can be inspired or reinforced by schools of performance. And if ever anybody proved the fallacy of performances based on the composer's intentions, it's Bach. What the music responds to isn't perimeters, but the cultivated vision that perimeters can provide. Consensus - what a boring idea - be damned.