The newest addition to the list of Performers To Watch is 11-year-old Chandra Fortune, who took second prize last weekend in the first annual Ylda Novik Memorial Piano Concerto Competition sponsored by the Washington Music Teachers' Association. Although eligible for the junior division of the competition, the young pianist competed in the senior division against performers six or seven years older and nearly took top place. The winner (who will perform later this season with the Washington Chamber Orchestra) was 16-year-old Charles Goldbeck . . . A piano competition sponsored by the Monday Night Musicales for pianists aged 17 to 26 will be held on April 24. For information, call 686-0238 . . . Next year's Naumburg Competition will be for violists. The finals, scheduled for May in New York, will be open to the public (write 144 W. 66th St., New York, N.Y. 10023) . . . The International American Music Competition will be vocal next year; preliminary rounds will be held all over the map in June (write Susan Clines, Carnegie Hall, 888 Seventh Ave., New York, N.Y. 10019) . . . And perhaps the most unusual music competition of the year will be the International Little People Music Competition (Box 477, Purchase, N.Y. 10577). They are looking for pieces of serious music, at least three minutes long, written by composers between the ages of 5 and 12.