Sheena Easton's first major American concert tour kicked off at the Merriweather Post Pavilion last night before a disappointing turnout of 3,200. The young Scottish singer pitted strength against weakness as often as she switched from ballads and medium tempo pop essays to hard-rock tracts. Easton, pert and personable, has a big, sturdy voice that belies her slight height, but it's a voice that sometimes loses in emotive range what it gains in dynamic power. The ballads succeeded because Easton didn't have to push herself, as she did on undistinguished covers of Kiki Dee's "Star" or Elvin Bishop's "Fooled Around and Fell in Love." At such times, she seemed like a curious blend of Pat Benatar and Julie Andrews.

Easton's best moments came on introspective ballads: the gorgeous "When He Shines," the haunting and bitter "You Could Have Been With Me" and the Jacques Brell-ish "Weekend in Paris," which she sang accompanied only by piano. On all three songs, Easton's delivery was heartfelt and direct.

Of course, it's the buoyant, irrepressible pop anthems like "Morning Train," "Modern Girl" and the gargantuan "For Your Eyes Only" that have made Easton an established star overseas and a fledgling one here. She would have made a more effective local debut had she not seemed so nervous, particularly in her somewhat stilted stage movements.

Easton is a charmer though, particularly when she lets her rich Scottish accent into the open. Since she's strictly an interpreter of other people's songs, she needs more consistent and challenging material. But Easton's pop career is just getting off the starting block and she has the potential to go for the long run.