Probably no scholar or performer has done more than Andrew Parrott (who is both) to keep Rifkin's idea alive. Over the years Parrott has argued eloquently for both the historical and the artistic legitimacy of performing Bach with one singer per part--and has produced some impressive recordings to back himself up. Several prominent Bach scholars have professed to be "waiting for the book" before giving their assessments of the Rifkin thesis; in time for the "Bach Year" 2000, Parrott has produced "the book"--and a very fine effort it is.
The Essential Bach Choir's virtues as a presentation and discussion of evidence may make it a bit difficult (though by no means incomprehensible) for lay people: the text is heavily footnoted, there are many musical examples, illustrations, and quotations (always given in the original as well as in translation); except in the prologue and epilogue, there is little discussion of the artistic merits of the one-singer-per-part approach (something for which The New York Times criticized Parrott). But this book isn't a critical essay on how good single-voice Bach sounds to our ears, it's a work of musicology intended to lay out the evidence and reasoning behind a thesis which has been dismissed, argued over, and viciously mocked for nearly two decades.
Parrott includes evidence commonly cited by the opposing camp; where warranted, he acknowledges their arguments, but more commonly he shows that the interpretation his opponents have given to the evidence is based on largely unexamined--and unfounded--assumptions. (Parrott quotes one esteemed Bach scholar who actually wrote, "Bach would have wanted..."--the sort of statement that academics in many disciplines would rip to shreds.)
What are these assumptions? That Bach's sacred works were quite naturally written for the medium of chorus-and-orchestra, like the oratorios of Handel, Haydn, and Mendelssohn (who revived Bach's vocal music in the mid-19th century). That those works are both the foundation and the summit of the entire choral-orchestral literature. That to posit such towering masterpieces as the St. Matthew Passion as originally meant for a little consort of soloists was literally unthinkable.
Parrott, following Rifkin's lead, argues that Bach's autograph scores and performing parts provide indications only for soloists. A very few works (all of which Parrott examines in detail) explicitly call for extra "choral" singers; for those works that do not, Rifkin and Parrott point out, it may not make sense to assume out of hand that Bach had or wanted such extra singers.
But isn't a choir by definition made up of several singers on each part? Not always--and Parrott presents much convincing material about the conventions governing vocal music in 17th- and 18th-century Germany that indicates otherwise. He also includes the complete text of Bach's much-argued-over Draft for a Well-Appointed Church Music, a memorandum the composer wrote to the Leipzig Town Council setting forth (depending on whom you ask) either the forces he wanted to perform his own music or the way he wanted the music program at the St. Thomas School and the church choirs for which he was responsible structured.
Since we have no rosters of performers--of the sort we have for some of Handel's operas and oratorios--for individual Bach works, this dispute may never be entirely settled. Also, as Parrott points out, modern-day performers and listeners are free to choose whatever medium for Bach's music satisfies them most--and musicians from Wanda Landowska to Angela Hewitt to Wendy Carlos have done so. But understanding Bach's sacred music surely requires understanding the medium for which he wrote it, just as understanding Beethoven's string quartets requires understanding that they weren't written for, say, a string orchestra. This book contributes immensely to our understanding of Bach's medium and milieu--and should be read by anyone who cares about Bach's music. --Matthew Westphal