Last year, after 13 years of performing Renaissance choral music, Seattle's Tudor Choir announced it was going into semi-hibernation. That was sad news, for the choir is very good, led by a true scholar-musician of this glorious English choral music, Doug Fullington. It had become a mainstay of Seattle's early music scene, perhaps the most vital of the local musical groupings. But not full hibernation, and there was the Tudor Choir last Saturday night, performing three works by John Taverner (1490-1545) at St. James Cathedral. It was doubly heartbreaking, because the music was so achingly powerful and because we'll hear so much less of it now. Just a couple hundred of us were there, in the magical acoustics of the cathedral. Just an hour concert, but one that left the choir exhausted and most of us emotionally drained, especially after the last work, "Gaude plurimum" ("Rejoice, greatly"), written by Taverner for his church choir in tiny Tattershall in Lincolnshire some 475 years ago. Rejoice greatly, indeed. Adding to the sadness was a realization that St. James is the perfect home for this group, even with a reduced choir of just eight singers. They sounded like 48, so beautifully does that space lift and extend and burnish and prolong each voice. For most of its life, the Tudor Choir has performed at St. Mark's, not many blocks to the north on Capitol Hill, but many miles short of being the perfect acoustical match for the choir. At St. Mark's, the choristers often felt underpowered and distant. St. James has its obstacles, to be sure, with requirements that the music all be sacred and complications about ticket sales. But it is a splendid space to sit in, and this fabulous choral music, one of the great achievements in Western music, blooms to full life in just such a long, even, reverberative soundspace. The choir will perform on some occasions now, when asked, but no longer do a formal season. The next big chance to hear them is December 22, when it will be the chorus for a period performance of Handel's Messiah, with Seattle Baroque Orchestra, at Town Hall. Why scale back? It just got to be too much work for Fullington, who has a fulltime job at Pacific Northwest Ballet and has been suffering from some arm pains lately. It was doing well, with money in the bank, but small arts groups are all a struggle in Seattle, where too much money and audience flows to the bigger organizations. So be it. Doug Fullington and the Tudors have given us unforgettably beautiful performances, to which one can only say, now, amen.