Sword play March 9, 2020 RWhitcomb-editor “Rock After Excalibur (cocktail swords and rock), by Matt Garrison, in the show “A Horse Walks Into a Bar,’’ at the Hampden Gallery at the University of Massachusetts at Amherst through April 12 The gallery says the show displays the work of “artists who continue to push the boundaries of fine art toward humor and wit.’’