Accompanist is a misleading -- even, demeaning -- term for a musician possessing the uncommon range of skills required to project great music in tandem. The first of these is an intuitive rapport making for hand-in-glove unanimity, allied with the unusual temperament to be, so to speak, second among equals. The stylistic awareness and technical resourcefulness demanded of any performing artist and a superb accompanist must be mercurially responsive. Possessed of these gifts in abundance, Geoffrey Parsons was, for nearly a half-century, a favorite keyboard partner to artists on...