By David Browne
January 21, 2000 at 05:00 AM EST

The beat thumps on unwaveringly until, with no pause, no warning, you notice it’s morphed into the altered groove of a completely different track — which will eventually be overtaken by yet another undulating number. And on and on and on. It’s the realm of the dance-mix tape, a world that in the last few years has ventured beyond the club DJ booths (and concomitant bootlegs) into record stores, via legit albums by groove-savvy electronica acts.

The fashionability of such collections is on full display in the dance bins littered with mix albums credited to Fatboy Slim, Prodigy’s Liam Howlett, the Chemical Brothers, Josh Wink, New York City radio personality and DJ Funkmaster Flex, and, most recently, Goldie. The discs serve two equally valuable purposes: They allow the DJs to show off their turntable skills while permitting the public to purchase a ready-made, nonstop album for the party in their club, home, or head. The latter seems particularly appropriate in the immediate-gratification world of e-commerce and MP3 downloads: Why expend energy making a compilation tape when you can just buy one?

Although each mix album conveys its own sensibility and personality, reflecting the tastes, quirks, and passions of the DJs who compile them, most fall into one of two categories. The first, heard last year in Howlett’s The Dirtchamber Sessions Volume One and now in the latest installment of the series On the Floor at the Boutique, is relatively straightforward: a ceaseless stream of more-or-less unaltered techno and R&B obscurities that segue into each other. The Boutique collections, named after the Brighton, England, club night that’s home to seaside sleaze and big-beat techno, kicked off in ’98 with a soul-drenched set by Fatboy Slim; this time, techno-punks Lo Fidelity Allstars step up to the booth.

Much like big beat itself, the Lo Fis’ parade of tunes is bustling and unsubtle, lurching from the vintage hip-hop of Boogie Down Productions and the Jungle Brothers to R&B jewels by the Tams and Felice Taylor. At its most enlightening — the swoop from the old-school robofunk of Humanoid’s ”Stakker Humanoid” to the manic rap preaching of Silver Bullet’s ”20 Seconds to Comply,” for one — the album ebulliently links past, present, and future. But its hip-hop-skip-and-a-beat jumble can induce headaches in the confines of the home.

The other style of mix album is ideal for such a setting. Songs are deconstructed, remixed, and blended together, making it impossible to differentiate them. The results are seamlessly hypnotic, and less frenzied, sets of chill-out music. Among the best in this genre are veteran British DJ Paul Oakenfold’s 1998 Tranceport, a narcotic compilation of trance techno, and the Austrian duo Kruder & Dorfmeister’s The K&D Sessions from the same year, which strips down Bone Thugs-N-Harmony’s ”1st of tha Month” to something resembling a dub instrumental. Either is as good as any album of original music released way back in the ’90s.

The second volume in the Tranceport series comes from another Brit, Dave Ralph, whose Tranceport II double disc extends the ambiance of Oakenfold’s disco-spaceship-to-Mars vibe. Although Ralph’s choice of tracks all fit into similar trance and house styles, they’re nonetheless a diverse and subtly ingratiating lot: the siren-like ”Feel So High” by Resistance D, the trippy swirl of ”Stella” by Jam and Spoon (a 1992 trance classic), the conga core of Oliver Lieb’s ”Subraumstimulation.” Since each has its share of filler, the two albums could have easily been condensed into one, much like Oakenfold’s. But then, parties do sometimes go on a bit too long, don’t they? On the Floor at the Boutique: B Tranceport II: B+

[BOX] Lo Fidelity Allstars On the Floor at the Boutique SKINT/COLUMBIA Dave Ralph Tranceport II KINETIC