A Mark Morris show—or two, in the case of this summer engagement—is always worth the trouble, if only to witness what the choreographer does with the music, which is his principal partner and always presented live at performances. The two-week Joyce outing features two premieres. For Program A (July 15 to 19), Morris turns to the composer and longtime Alaskan John Luther Adams for a harp and percussion adaptation of Indigenous Alaskan dances. In their walking pace and the glow that the notes sustain long after they’re struck, the short numbers bring to mind the work of the late composer and gamelan devotee Lou Harrison, which drove Morris to forge an unlikely but bewitching bond in his dances between force and poignancy. He is at his best when the music is opaque, spacious, deviates from pattern, or curdles harmonies—in short, leaves something to be desired, though beautiful in its unfinishedness. The unsung maverick of the stride piano, Fats Waller’s teacher James Price Johnson provides the music for the second premiere, on Program B (July 22 to 26). Decoratively delightful and rhythmically tricky, Johnson is likely to prompt Morris’s musical punning, which can be very fun and funny. —Apollinaire Scherr