Something funny is going on at Top 40 radio. The hook of the summer is an unusual lobotomized drone ''la da dee, la da da'' in Crystal Waters' ode to human resilience, ''Gypsy Woman (She's Homeless).'' Flip around the dial and you're likely to hear a metal band turning into acoustic balladeers (Extreme's ''More Than Words''), an eccentric British club hit (EMF's ''Unbelievable''), or a song that fuses rap and '50s doo-wop into a sexy whole (Color Me Badd's ''I Wanna Sex You Up'').
Granted, the predictable leading single of the summer is Paula Abdul's gauzy ''Rush Rush,'' and you'll also hear more than a fair share of the dance- club beats and soft-rock ballads that have dominated Top 40 for the last few years. But thanks to a slide in Top 40 ratings, program directors are willing to take a few more chances to bring back those listeners who may have fled to stations offering soft rock (Adult Contemporary) or classic rock. As a result, it's now possible to turn on the radio and not think you're spending the day in an aerobics class. Even several months after its release, it's still an unexpected thrill to hear R.E.M.'s luminous ''Losing My Religion'' sandwiched between standard Top 40 fare like Bryan Adams' banal ''(Everything I Do) I Do It for You'' and a piece of Fuzak like Candy Dulfer and David A. Stewart's instrumental ''Lily Was Here.''
In one sitting in front of the radio, you can hear cultures collide: Cher's undeniably hooky corporate rocker ''Love and Understanding,'' followed by the Beatlesque if cloying Extreme record, followed by D.J. Jazzy Jeff & the Fresh Prince's unexpectedly sultry ''Summertime'' and Rythm Syndicate's ''P.A.S.S.I.O.N.,'' the best rip-off of a style (in this case, the new jack swing of Guy and Bobby Brown) since Ready for the World's 1985 Prince clone, ''Oh Sheila.'' This may not yet be a return to the 1983-85 era when Michael Jackson, Prince, Bruce Springsteen, and the giddy soundtrack pop of Footloose battled it out on the pop singles charts. But anyone who thinks Top 40 is formulaic and repetitive just isn't listening.
With any luck, you'll also be hearing more of the year's two smartest hits. Seal's ''Crazy,'' a British hit burrowing its way up the U.S. charts, is the sound of desperation; when the black British pop idol sings, ''We're never gonna survive unless we get a little crazy,'' he sounds as if he's giving in to the madness of the world. Yet the song's eerie, echoey chorus, drenched in synthesized Brit-soul, brings you back every time. And Kirsty MacColl's ''Walking Down Madison'' merges the British singer-songwriter's fresh-faced singing style with a drum-machine beat and a cameo by a rapper. It's as if Lulu or some other '60s Swinging London pop star went for a stroll in the South Bronx.
Besides reminding us that Top 40 can still bring disparate ages and races together despite radio's current fragmented state, the music being heard this summer is a reminder of something else: Nothing beats a pop single. Even with the ascendancy of videos, there remains something wonderful about a song's infectious chorus or a unique production twist, something that makes the world seem a better place. No matter what time of year, we can never have enough reminders of that.