Tufts University Art Galleries presents the third of four player piano sessions featuring the boundary-defying work of composer Conlon Nancarrow, in conjunction with the current exhibition “Impossible Music.” Nancarrow was one of the first composers to work with “auto-playing” musical instruments, particularly the player piano, because of its ability to perform scores that exceeded human ability. Nancarrow’s early work was characterized by its extreme technical demands, only rarely performed to his satisfaction. He turned to machines as a means to faithfully hear his compositions, which are complex arrangements of tempo, rhythm, and pitch. The program, which features four compositions from “Study for Piano,” will be presented for the final time on Friday, April 4.