By Jim Farber
Updated January 25, 1991 at 05:00 AM EST

At a time when adult pop singers regularly mistake showing off for true virtuosity (think of Whitney Houston and Mariah Carey), Celine Dion comes as a welcome relief with Unison. This 23-year-old Canadian singer isn’t obsessed with displaying how many notes she can hit and how hard she can hit them. True, Dion’s voice is hefty and her phrasing skilled. But on her first American LP her singing remains tastefully unadorned. Better yet, Dion never attempts to bring off styles that are beyond her. While Whitney and Mariah give us ersatz gospel and supper-club soul, Dion concentrates on mainstream, grown-up pop. Tracks like ”If Love Is Out of the Question” and ”The Last to Know” are lush vehicles, filled with routine hooks that Dion’s distinctive voice raises to a higher level. Dion does falter when she moves outside of plush ballads (as in the forced dance-club mix of ”I Feel Too Much”). But within her metier, the singer proves an important point: that even the most naturally generous voices can benefit from a little modesty. B