It was Bach all day Saturday at Wolf Trap and Back was all wet.

You would have thought the musicians of the Washington Back Consort were performing his cantata, "Glide along, you playful waves! No rush swiftly along!" rather than the Magnificat. After sending torrents of rain most of the morning, the weather deities continued to shower Wolf Trap's lovely green lawn most of the afternoon. Some of the time the rain even blew gently into the shed, spraying a persistent mist over the listeners who had come to hear the Back marathon. There were several hundred loyal fans when the concert began and a small but steady stream of brave souls swelled the audience during the next four hours. Had the day been fair there surely would have been thousands.

Because the high humidity that enveloped the day is a notorious foe of both string and wind players, it is much to the credit of the musicians in the consort that they could open the afternoon with the Fourth Brandenburg Concerto and give it a sense of vitality as well as accuracy. Jody Gatwood's violin and solo readers in the hands of John Lagerquist and Robert Kraft never faltered in tone or intonation. With Reilly Lewis supplying excellent backing at the harpsichord, it was an auspicious opening. If, in the course of the concerto, there were times when the pitch of the ensemble fell off the mark, it was entirely forgiveable.

Incidentally, the level of sound was better -- more natural -- at the beginning of the concerto than it was after a technician walked in, listened a moment, then signaled the engineer at the controls to bring up the volume.

Charles Curtis' playing of the C Major Suite for unaccompanied cello must be counted an even greater triumph in the face of the antagonistic weather. There is no tougher test for the cellist than to sit on the bare stage with nothing but his unsupported cello and work his way through any of the Bach suites. Curtis managed the difficult feat as if he were playing temperature and humidity. The long lines sang freely and the dances were marked by a fine inner rhythmic pulse. Having nothing to do with the weather were some recurring scraping attacks that should be ironed out.

For the Magnificat, Lewis turned over the continue duties to organist William Neil and took the conducting platform. It was a real shame that one of the true downpours of the afternoon heralded the opening of the great work. But the chorus and orchestra upheld the good standards by producing admirable tone in tune. Lewis likes a light, clear choral sound, which is appropriate some of the time, and his singers gave him precisely what her requested. However, a greater sense of solidity -- not necessarily volume, but a kind of exaltation -- is essential in the grandest passages, and this was lacking.

The solo trumpet was a joy throughout, and William Skidmore's double bass under the bass arie "Quia fecit mihi magna" was sheer delight. The solo singing was an unhappy reminder that first-class Bach singing is not easy to find among young vocalists these days.

For the afternoon's finale, harpsichordist Anthony Newman and the Chromatic Fantast and Fugue. He set some kind of speed record in the Goldbergs, playing them in 42 minutes flat, obviously avoiding all the repeats. It was not a problem of speed alone, however, that made them the day's one failure. Rarely has the great music sounded so glib, so mechanical, so soulless. Newman should have taken a leaf from the spirit of that which preceded him.