The performance by the Mark Morris Dance Group at Summerfest last week was like a loaf of artisan rye bread—dense, complex, chewy. The evening at the Conrad Prebys Performing Arts Center was so packed with dance, music, and ideas, I would have like multiple viewings: once to focus on Morris’s choreography and brilliant movers, once for the world-renowned Summerfest musicians, and a third time to lose myself in the thrilling voice of countertenor John Holiday.