01:00 AM EST on Thursday, March 16, 2006

BY CHANNING GRAY
Journal Arts Writer

When Bach died in 1750, he left behind an extraordinary legacy: hundreds of sacred cantatas, the B Minor Mass, the Well-Tempered Clavier and the Brandenburg Concertos. But no work is more controversial than The Art of Fugue, his last, incomplete word on the subject of contrapuntal writing.

Scholars to this day continue to debate whether the score was meant as a didactic guide to fugal writing or a practical piece destined for performance. But for what instruments? Bach left no indication.

When it is performed, which is rarely, it is usually played on the harpsichord or organ -- although it has been arranged for orchestra, saxophone quartet, and just about every other instrumental combination.

Tonight and tomorrow night, the Providence String Quartet will tackle selections of this monumental work. And the performance will be accompanied by a computer-driven video intended to make clearer the complex structures of the piece.

Complex, then more complex

What is a fugue, anyway? Think of it as a round, only more involved.

Remember, in grade school, having the classroom divided in two sections? One side would take up Row Row Row Your Boat, and soon the other half would join in, so that both tunes were being sung, only not in synch.

Well, a fugue is sort of like that, but much more complex.

The composer comes up with a theme or subject. As that is being played, the same tune enters at a different, usually lower pitch. Then it appears a third, fourth, perhaps even fifth time, all staggered, forcing the performer to keep a number of musical balls in the air at once.

But if that weren't enough, fugal subjects go through all sorts of permutations. Composers often turn the main theme upside down, speed it up or slow it down, so that while the subject might appear right-side-up in quarter notes in the upper registers, the bass line might be upside down in half notes.

Fugues, you could say, are fascinating puzzles that, at their best, boast mind-boggling architectural intricacies, but are still lovely, compelling pieces of music.

Although the fugue is basically a Baroque-era invention, popular in the 17th-century, composers in the 18th and 19th centuries, even a few in the 20th, have written fugues. Beethoven used them in his late quartets and final piano sonatas; Mozart wrote several keyboard fugues and, tradition dictates, wove them into his Masses. Brahms wrote a famous set of piano variations and fugue on a theme by Handel.

But it was Bach who perfected the art form, which he continued to employ long after it went out of style. While The Art of Fugue has a somewhat abstract feel to it, it is also ravishing music, even to listeners who don't entirely understand all that's going on in the music.

"If it were dull to the ears," said Sebastian Ruth, a violinist with the Providence Quartet, "you could say it was just an exercise. But it's so exciting."

An unfinished work

It was sometime in the early 1740s when Bach set out to write this definitive statement on the fugue.

The hour-plus work is based on a single subject transformed in myriad and ingenious ways with each new fugue. Sometimes it is seen right side up, sometimes upside down or backward. There are also triple fugues, which use three different subjects eventually woven together in a way that somehow makes complete harmonic sense.

Bach was to end the set with a monumental quadruple fugue, but never finished it, or at least it has come down to us in incomplete fashion. The fourth theme never appears, and the fugue breaks off mid-phrase.

The third theme, however, spells out the composer's own name -- B-Flat, A, C, H, which is B natural in German notation.

"The guy knew what he was doing," said Ruth.

Ending with a simple choral

In all, there are 14 fugues and four canons, which are more basic forms of counterpoint in which one theme chases another.

For its concert tonight at the Providence Athenaeum, the quartet has picked a sampling of fugues that show off different treatments of the subject.

The selections demonstrate straightforward renderings, inverted subjects, and so-called stretto techniques, in which the entrances of the theme are compressed and piled on top of one another. In Fugue Six the second voice comes in on the second bar, but is inverted and twice as fast as the main theme.

Two triple fugues follow. Twelve is one of the remarkable "mirror" fugues, in which Bach wrote two fugues, the second being the exact reflection of the first.

The quartet ends with one of the canons, which uses augmentation or elongated note values and contrary motion in the counter theme.

Then comes the final triple fugue, intended as a quadruple. It was believed for a long time that the fugue broke off abruptly because Bach died. That may not have been the case. Some believe the fugue was finished but the manuscript lost.

Another opinion holds that it was left unfinished as a sort of puzzle, a challenge for composers and performers to come up with their own solutions. Bach and other organists of the day would often indulge in contests, where one player would begin a fugue, then pass it off to a competitor.

Instead of using one of the completions for the last fugue written after Bach's death, the quartet will perform a simple choral that Bach wrote at the end of his life -- Wenn wir in hochsten Noten sein (When we are in greatest need).

Video accompaniment

As for the video component, while the quartet performs, abstract colored images, each representing a theme, will appear on a screen. The video was prepared by URI film and video Prof. Sheri Wills. The project has been in the works for the past couple of years.

Ruth, violinist for the quartet, said that Wills has used close-up shots of light dancing off colored glass to represent the material found in the fugues, although it is not obvious at first what the images are. Only later, as the camera pulls back, can you see through the glass. When the BACH theme appears, a portrait of the composer is visible.

The video is not set in stone, however. Wills will be on hand, manning a computer so that the video images will mesh perfectly with the music. It would be a little hard for live music to match an inflexible tape.

Bach wrote The Art of Fugue in open score, with one line music per staff, and he gave no indication of loudness or softness, which poses a problem, said Ruth. One can try to spotlight only the material in the musical fabric that is interesting. But it is all interesting. Decisions have to be made.

Ruth said Wills tried, like Bach, not to bombard the listener with ideas and images. Although Bach, he said, did "close the book" on the subject of the fugue.

"He must have known that at some level this was for posterity," said Ruth, "even though that was not a popular idea at the time. You wrote for the next gig.

"But this says everything that needs to be, and can be, said about the fugue."

The Providence String Quartet performs excerpts from Bach's Art of the Fugue tonight at the Providence Athenaeum, 251 Benefit St., Providence. Reception 6:30, performance 7:30. Call (401) 421-6970, ext. 28.

The Bach will be repeated Friday with a free spaghetti supper at the West End Community Center, 109 Bucklin St., Providence. The concert is free and will include the double-bass quintet of Dvorak with Max Zeugner. Dinner is at 6 p.m., the concert is at 7 p.m. Call (401) 861-5650.

cgray@projo.com / (401) 277-7492