William Byrd and John Bull The Visionaries of Piano Music Kit Armstrong, piano  Deutsche Grammophon CD   In The Visionaries of Piano Music, Kit Armstrong plays two of the greatest English keyboard composers active during the reigns of Elizabeth I and James I on the modern piano, aiming to show what he calls “a seamless line of development” between this repertory and more recent music written explicitly for the piano. William Byrd (ca. 1540-1623) and John Bull (ca. 1562-1628) wrote for very different instruments from the piano, the harpsichord and its smaller companion the virginal; Christofori developed early versions of