Van Koevering ran the Island of Electronicus, a nightclub in St.
Van Koevering, who marketed the instruments nationwide.
Moog built one of the first portable synthesizers for Mr. Moog through their mutual fascination with theremins, electronic instruments that emit different tones of varying loudness depending on how the musician's hands move in and out of an electrical field. One high school project involved an instrument that was played by turning a flashlight on and off. Van Koevering began inventing his own instruments as a child. The son of a man who traveled around state fairs in the Midwest performing on novelty instruments, Mr. Van Koevering never needed such learning aids.
For example, Seer Systems, of Los Altos, Calif., calculates that a musician seeking the latest in sound-synthesizing technology would have to buy four separate instruments costing a total of more than $12,000 to approach the capabilities of its $495 Reality software program, which runs on Windows 95. And the latest software for high-end personal computers provides music-synthesizing capabilities that makers of digital instruments will be hard-pressed to match. Even home computer systems can produce great sounds if they are linked to high-quality amplifiers and speakers. Moreover, the performance advantages of the more expensive digital instruments may be waning. One challenge is that simple 88-key keyboards costing just a few hundred dollars offer much cheaper fun. Sales of digital pianos have leveled off at about 50,000 units annually in the United States in recent years. Such systems are playable, but they often end up being used largely as classy living room or parlor furniture capable of reproducing preprogrammed music from CD's or remote broadcasts. Indeed, some buyers for the digital instruments are barely musicians at all instead, they are looking for what are in essence old-fashioned player pianos on electronic steroids. Gauging what the keyboard market wants is not easy. Such instruments sell for $2,000 to $11,000, depending on the cabinetry, sound systems and other features. It also reaches out to beginners with an Anyone Can Play program that makes sure the only keys sounding notes when struck by the right hand are those that harmonize well with whatever chords are being played by the left.
The company sells its Mark series of digital pianos with prepackaged education software, like Edugames, which tests the player's ability to match pitches. Kurzweil and others also recognize that while children do not buy pianos, they are often the reason that their parents do.
''The home side is always a little behind the professional side, but screens are coming,'' said Jean Bellefeuille, head of professional sales for Kurzweil. Even more impressive, the Van Koevering piano can handle multimedia music software - a music learning program, for example - that until now has been used only on home computers with plug-in keyboards. The touch controls on the screen allow the reader to create and mix multiple tracks of music, without the knobs and switches used for such composing on other digital pianos. The player can use a video score, turning the pages with a foot pedal. The monitor eliminates the need for a hard-copy score for Beethoven's ''Moonlight'' Sonata or any other piano standard. Where a player would normally put the sheet music, there is a touch-screen monitor, similar to a personal computer monitor, that can display full-color, full-motion images. Van Koevering, 57, is betting on a computerized ''interactive piano.'' The instrument, which he began visualizing 10 years ago, has a hard disk, four Pentium microprocessors and a modem, for direct Internet connection. And, in the case of the electronic synthesizer, it led to a friendship with the inventor Robert Moog and years of work helping popularize that revolutionary musical technology. DAVID VAN KOEVERING has spent a lifetime demonstrating ancient or odd musical instruments and exploring new ways to make music.