In the middle of "Bright Nights," the final track of Koop's CD Waltz for Koop, Yukimi Nagano sings in her strange English (a vaporous mix of Japanese and Swedish accents) these lines: "Bright nights/City lights/And we won't leave soon/The DJ kicks/Jazzy licks/A favorite tune/Afro-blue/Cocoa hue/Midsummer moon/Bright nights/City lights/And we won't leave soon." This intoxicating infusion of codes--cool DJs, cool jazz musicians, erotic city nights--best describes Koop's approach to music: They don't make jazz, but instead reproduce its moods and signs.

While listening to the nine tracks on Waltz for Koop, you're struck by their familiarity; you've heard them before, but you can't determine when or where. Your memory tries to locate the source, the original, but it never finds just one song--it runs up against a blur of numerous jazz tracks. The confusion, the mystery, is caused by this: With the exception of "Relaxin' at Club F****n," the songs on Waltz for Koop sound live, when in fact they are illusions composed of samples.

"A lot of people think it's a live thing, but it's actually not," explains Magnus Zingmark over the phone. (He and Oscar Simonsson make up Koop.) "Every song samples something.... We made a big effort to make it sound relaxed and like a live thing, but actually all the tracks are programmed."

Zingmark and Simonsson are not jazz musicians but jazz DJs or, as Europeans like to put it, jazzheads. "We play instruments as well," Zingmark says, "but it's about composing tracks rather than playing instruments. The way we compose tracks is we find something we want to sample and then we play around with the piano or the keyboards, find the cord structure, write some lyrics, and then bring in some more samples."

By means of electronic devices, the music of a distant era (1955--1964) comes back to life. But this is no ugly or clumsy jazz-Frankenstein; Koop's monster is as impressive, as enchanting, as bright city lights on a midsummer night.