To monitor vandalism against this year’s Martin Luther King Jr. exhibit, surveillance cameras were installed two weeks ago in Lobby 10. The cameras are not actively watched, but the video is stored, the security office said.

MEDFORD, MASS. — There are videos showing off card tricks, horsemanship, jump rope and stencils — and lots of rap songs, including one by a young woman who performed two weeks after oral surgery, with her mouth still rubber-banded shut.

Because of an editing error, a front-page article Friday about the Kendall Band identified two of the Band’s three instruments by the name “Kepler.” Kepler is the large metal ring. The rumbling sheet of metal is named “Galileo,” not “Kepler.”