"HERE COMES the band with a brand new sound . . . it's the sound of a robot generation."

If they ever get big, their contract should be a pretty much nuts-and-bolts affair: They won't need any fancy pre-concert dinners; no liquor, just juice; if the hotel is full, well, they can always park themselves in the garage.

They're shorter than your average rock-group members, all about Roger Daltrey-size. Lead singer Astro has pretty good microphone technique and scoots around the stage. Apollo, on lead guitar, isn't quite as flashy but he and drummer Retro keep a steady beat, while bassist Electro just stands there like John Entwhistle, keeping up his bottom end. The latest addition sits behind a standard keyboard and pumps it up; he's so new he doesn't have a name yet. "They" are the Nuclear Diode Robot Band and they'll be performing tonight at the Bayou.

Happily, the band is not into heavy metal but into the electro-pop rock symbolized by their original theme song, "Robot Man" (courtesy of the local human rock group, Jetz). Like most rock bands, they've come together over the years, literally and figuratively (they have more than 1,000 parts). Astro and Retro were the first, about five years ago. Their backgrounds? Astro used to be a weather satellite, while Retro used to be a pratice bomb. Their Brian Epstein is Tim Pace of Falls Church, who runs the light, sound and video systems at the Bayou when he's not tinkering in a house full of NASA surplus equipment and odds and ends saved from various metropolitan junkyards. As the band performs to pre-recorded tapes, Pace positions himself behind a former missile launching panel, with the controls now directed at making the band members walk, spin, sing, play, twirl their antennas, light up and generally make a spectacle of themselves--like most rock 'n' rollers.

The 36-year-old Pace, who has worked as a light man for such folks as Jimi Hendrix, Rush and the Kinks, has built his band slowly; tonight will be the group's first official concert, although the Diodes have made appearances at private parties, computer fairs and electronics conventions. Each member is, of course, custom made. Pace has simply to walk around his basement looking for parts; he has piles of parts, cabinets full of every kind of motor. "I'll choose one and say, 'Well, this looks good for his hand.' " His garage is wonderfully cluttered, and in his backyard, there's a used shuttlecraft full of yet more parts.

He'll use anything from a weather satellite chassis to direction finders to laser gears to digital missile readouts. Pace gets most of the stuff from government auctions, where, ironically, his high bid gets material originally built on low bids. The Diodes, Pace says, are really cheap, worth maybe $500 in parts. "But I couldn't put a price on them . . . and nobody else could do it." The band was temporarily unplugged, as Pace spoke--except for Astro, who is radio-controlled and was off having his batteries charged.

Blame all this on the electric trains of his youth, Pace says, but also give a little credit to "Star Trek." In fact, an exact duplicate of the control panel of the starship Enterprise is part of his basement recording-video studio, and his driveway is occupied by a huge van called, humbly, the SS Enterprise. It, too, is filled with control boards and panels and laser guns; in fact, it looks as if it could take off at any moment. Pace used to show off his working duplicate of R2D2 until a cease-and-desist letter came from George Lucas' lawyer. Now R2D2 is his copilot.

Pace admits that "there are a lot more sophisticated robots than these. They're toys, mostly for kids." There is, he realizes, a robot band at Disneyland, but it's bears, not a "machine band." He feels he's got the first. Incidentally, Pace will be in the shadows on stage at the Bayou tonight. He's easy to spot: He's the tallest and he has hair.