Putting together a high-tech garage band

Somewhere, four computer-savvy kids obsessed with music are sure they will be the next big thing if they could only get the right gear. Here are the musical instruments they might want. The Variax 700 digitally models an array of 25 vintage rock-and-roll guitars using offtheshelf components and custom software. The adjustable saddles on the bridge of the Variaz 700 hold the piezoelectric pickups (the shiny silver insets the strings cross over). They detect string movement and translate it into an electrical signal, which is then converted to a digital signal and manipulated. The V-Synth from Roland Corp. features several innovative user interfaces for manipulating sounds and waveforms. The LCD in the center, for example, lets players change filters, sound source, and other functions. Players can also change two parameters, such as tempo and pitch, by moving their fingers on the Time Tip Pad. The art of making musical instruments has long since gone beyond mere woodworking and other refined crafts. Digital signal processing and bandwidth are now king. And some companies are using the latest and greatest in hardware, software, and modeling techniques to faithfully replicate classic rock-and-roll instruments. But they're also coming up with new, otherworldly sounds. And there are still some craftsmen among the technophiles. Every make and model of guitar differs slightly in its sound and tone. Some, like the '58 Gibson Les Paul Standard and '60 Fender Telecaster, have earned cult status as " classic" rock-and-roll instruments. As these instruments grow in popularity, the price tags on them grow as well, putting them beyond the reach of all but the wealthier musicians. Engineers at Line 6, Agoura Hills, Calif., aware of the economics of vintage instruments, decided to build a guitar, the Variax 700, that would exactly replicate the sounds of two dozen or more famous guitars and switch between them quickly and effortlessly. The engineering team had a few years experience in modeling, but it was mainly in digitally mimicking tube-based amplifiers. So before they could build the Variax, they had to discover what it was in a guitar that contributed to its overall sound. "We broke down the various elements responsible for a guitar's tone into basic components, then described them mathematically with algorithms," says Pete Celi, senior designer at Line 6 and responsible for the digital signal processing in the Variax. "The main components in an electric guitar are the electromagnetic pickups, at least one per string, and the body or physical structure of the guitar." Pickups, the sensors that detect what the guitar strings are doing, are simply coils of wire wrapped around a magnet. They can be described by an inductor (the coil) and its magnetic losses, some parasitic capacitance, and the dc resistance of the wire. So the coil can be represented as a four-element circuit: two resistors, a capacitor, and