Servant, the popular rock-gospel group that will perform tomorrow night at Northwood High School, is something of an enigma in the world of contemporary Christian music. For one thing, the group has the biggest show on the gospel road today: 10 tons of equipment, including a laser and light show and fog machines, a wall-to-wall quadrophonic sound system carted around in a 40-foot semi. Audiences tend to stand up and get involved in the shows, something that doesn't happen in the generally staid gospel circles. With searing guitar, booming drums and new wavish synthesizers, Servant doesn't look or sound that different from any rock band: It's just the message that's different.

After starting its career in churches seven years ago, Servant also played in a number of West Coast bars. "We even set some attendance records," says bassist Owen Brock, who founded the group and whose wife Sandie is one of the Servant vocalists. Back then the group did a mix of old rock 'n' roll and gospel-rock numbers and talked to people--the missionary side--between sets. "As the years went by we got better, playing five hours a night, five nights a week." Four years ago, Servant recorded its first album in the same studio used by Loverboy and started touring, something it still does to 10 months of the year.

"We feel that the music we write is really compatible with what's happening in the secular music scene," Brock says. "We're trying to represent a better standard of Christian music, something that relates more to today. We want to provide an alternative for people who like rock music and who enjoy the medium and the excitment--face it, a rock show should be exciting--but at the same time, they don't want the drugs or the grossness that can pursue the secular rock artist.

"Gospel music is changing, at one point it was 10 years behind what was happening, I don't thing that's true any more. We listen to Police and Missing Persons, that's where we're drawing our expertise from."

Now in the middle of a 94-city tour that will occupy them through next April, Servant is also doing something most bands would never dream of: giving away copies of its new record, "Caught . . . in the Act of Loving Him," to everyone who comes to its concerts. The total by road's end: 200,000 copies.

"It's our inflation-fighter, a deal they couldn't refuse," says Brock. "We felt our music was the best we'd ever done and we wanted what we had to say to go into that many homes."