Marcia Kravis is the rare conservatory-trained musician who loves it when her audience falls asleep. Thursday afternoons you can find her sitting in a corner of the emergency room at Thomas Jefferson University Hospital in Philadelphia, tapping a hammered dulcimer to set a mood of tranquility. She studied harpsichord at the New England Conservatory of Music and, after years of performing and teaching, trained as a music practitioner. She picked up the dulcimer in part because of something she'd heard in music-therapy class. She found the hammered dulcimer relaxes people who are stressed without suggesting the heavenly gates.