The first time Robert Hill set a piece of Lowell Liebermann's music to dance, he was nervous. What would the composer think?

“With Mozart you don't have to worry,” Hill said recently of the task of choreographing music of a living composer.

Unlike Mozart, Liebermann was not only alive and well, but he also was living — as Hill would soon learn — a block away from his own home on the Upper West Side of Manhattan.

The two “neighbors” were about to meet in the studios of the American Ballet Theatre.