GREAT BARRINGTON -- Kenneth Cooper says he isn't second-guessing Bach. He's only doing what Bach did.
Cooper will lead the Berk shire Bach Ensemble in Bach's complete set of Keyboard Inventions on Sunday afternoon. He'll play the 15 two-part inventions on the harpsichord. Then he'll join six wind and string players in his scoring of the 15 three-part inventions ("sinfonias") for larger forces.
The concert, which opens the Berkshire Bach Society season, begins at 2:30 in the First Congregational Church. It's the society's annual "Bach at Zimmermann's" program recalling the Leipzig coffeehouse where Bach led his Collegium in performances of his chamber pieces.
Enhancements of Bach are nothing new for Cooper, the society's music director. As followers of his Berkshire ventures such as the annual New Year's Eve bash know, he frequently adds trimmings to the "Brandenburg" concertos and other compositions.
"I've been doing this for more years than I can remember," he recalls, "because, you know, Bach and Handel, and even Mozart and even Beetho ven, didn't hesitate to rescore some of their things if they felt the necessity for it, or somebody paid them for it. But often it was because the occasion changed and they needed something a little different.
"Or sometimes with Bach," adds this Bach scholar, "you have the feeling that he looked at the score again and thought, "Hmm, I can do more this time."
"Inventions," for Bach, means ideas of the musical kind. It's spelled out in his in troduction to the compendium.
"Bach wasn't given to verbiage very much," Cooper noted in a phone interview. The explanation preceding the inventions, however, shows "how he was concerned on a variety of levels about different things, and he knew that students, including his children, would gather different kinds of things from it, depending upon what level they were at."
Bach cites three pedagogical objectives of "candid instruction," step by step: First, "how to play independently in two voices." Then, playing in "three obbligato parts, meanwhile arriving at good inventions [ideas]" of the players' own. But, foremost, achieving a "cantabile" [integrated] style of playing, and along with it, acquiring "a strong foretaste of composition."
Bach shows kids "what a good compositional idea consists of," Cooper said. "And, boy, there are plenty. You learn something every day. I've been through years of years of listening to gorgeous Bach works, and everybody else's, and you turn back to these pieces among others, and yes, there are wonderful ideas in them that you wish you had thought of."
In his rescoring of the second keyboard set, Cooper has mostly reassigned the existing three lines to three winds (flute, English horn and bassoon), three strings (violin, viola and cello) or some combination of winds, strings and keyboard. Two of the last inventions seemed to call for more elaborate treatment. These he turned into mini-concertos.
Bach frequently did this kind of thing to his own music, Cooper points out. He cites the familiar third "Brandenburg," which is for strings only. Needing a movement later on for a cantata, Cooper says, Bach borrowed the concerto's first movement and added winds and a tripling of strings.
For Bach Society performances of the third "Branden burg," Cooper goes a step further and adds the winds to the finale. It's a natural progression, he says. He also interpolates a slow movement by Bach.
Elsewhere, he adds such em bellishments as drums in the first "Brandenburg." Improvi sa tions are an important ingredient.
"You try and do the best you can what Bach would have liked done," he says. "Though it's a lot of work, it's very much fun to imagine that. I'm never going to say this is how Bach would have done it because, of course, this is what we don't know. But we try and come as close as we can."
As far as Cooper knows, this will be the first complete performance of the inventions in the Berkshires -- certainly the first with his recently finished version of the second set. He is leaving some of the final details to be worked out when the players get together in the Berkshires. He welcomes the spontaneity of changes happening on the spot in rehearsal or performance.
Though Cooper plays the harpsichord, his ensemble plays modern instruments.
"The fact that they're great artists is more important to me than anything else -- more important to me than what instruments they play," says Cooper, who is also a conductor and fortepianist. They're all veteran players, he says. They're also "profound Bach lovers."
So, you might say, is Ken neth Cooper.
What: "Bach at Zimmerman's: The Inventions" (Berkshires premiere). Berkshire Bach Ensemble. Kenneth Cooper, conductor, harpsichord
Who: Berkshire Bach Society
When: 2:30 p.m. Sunday
Where: First Congregational Church, 251 Main St., Great Barrington
Tickets: $30; Berkshire Bach Society members -- $25
How: At the door
Additional information: www.berkshirebach.org