OH YoU BeAUTiFuL BaBY Barbara Trun- sky, with 8- 1/2-month old Zachary, who already shows signs of being a young Mozart. With a song in their heart, babies take center stage. 5/29 1998 78 Amy Grosinger tells us daughter Samantha, 15 months, is really on the ball. Each week, babies and their mothers get together for a morning of music, fun and play at Congregation Shaarey Zedek's Applebaum Jewish Parenting Center. The class, "Music & Movement," for children 3 months and older, is taught by Lynn Breuer. So far, babies have had nothing but coos and aahs for the course, which nursery school director Janet Pont says, "is a at of fun. Everyone has a wonderful time."