THEY were plastic bits of melody. On Friday two weeks ago, on the darkened stage of Graha Bhakti Budaya of the Ismail Marzuki Art Center in Central Jakarta, the soprano sang the same phrase from beginning to end. Yes, bits of the same melody, but with a surprising level of variation, suddenly rising one octave higher to cruise along the same path and, rounding in small circles, turn in the opposite direction before falling on the final notes.