A chorus of grasshoppers at the finger tips

Imagine playing a trumpet into a microphone and getting from the speaker not the blare of a trumpet but the chords of a grand piano. Or playing a saxophone that sounds like a violin. Or strumming a guitar whose riffs sound as though they were produced by a full orchestra. Today, such transformations are far from make-believe. MIDI (Musical Instrument Digital Interface) is turning musicmaking inside out with the interfacing of instruments.

The process is simple: Music played into a microphone or from a specially designed instrument -- most often a keyboard -- is like a signal. That signal is instantly translated by computer into a different language known as MIDI commands.

These commands are sent to a synthesizer that ``understands'' them and produces the music in a different way -- as another instrument or sound.

``The violin part in one of Bach's Brandenburg concertos could sound like it was being played on banjos, trombones, a chorus of grasshoppers, or laser blasts,'' explains Mitch Farber, vice-president of Ciani Musica, a music production company in New York City.

Some instruments, called controllers -- specially built guitars, drums, keyboards, and a clarinet-type instrument called the lyricon -- produce only electronic signals, not acoustic sounds. The musician plays the controller, while a sound generator, or synthesizer, actually makes the sound.

So a musician who only knows how to play the piano can, in effect, make music on any instrument -- even drums -- just by playing a controller keyboard.

MIDI began in 1983, when synthesizer manufacturers such as Sequential Circuits, Yamaha, Roland, and Korg realized they could sell more instruments if they made them compatible.

Now synthesizers and computers can ``talk'' to each other or give and receive commands. From one keyboard, a musician can control 12 or more synthesizers at the same time, combining layers and layers of sound.

Robert Moog, a computer music pioneer, hails MIDI as ``the dominating force in the field of electronic music.''