If there's anything the Billboard Top Hits compilations documenting 1985 through 1989 indicate, it's that the period covered wasn't exactly pop music's most glorious era. Not only was there a lot of rock music being made that aged almost instantly; the mainstream had yet to fully embrace rap music, and a lot of the production qualities infiltrating nearly every genre of music ? the overbearing use of mid-range and the blazing guitar solos, for two ? haven't aged well at all. Still, these cheap and concise compilations function as accurate scrapbooks of the years being covered, and they're especially fascinating for pop fans who like to keep tabs on trends, changes, and developments. The ten songs that make up the 1989 installment of Billboard Top Hits are, for the most part, ballads ? whether fitting easily into the teen pop, hair metal, or adult contemporary realms. Warrant's "Heaven," Bad English's "When I See You Smile," Richard Marx's "Rig...