On the rainy night before Halloween, the Mount Holyoke Symphony Orchestra welcomed its first in-person audience since March 2020 to the 11th annual Monsters’ Ball. The balcony of Chapin Auditorium was practically filled to the brim with attendees, most of whom dressed up in Halloween costumes for the occasion. Instead of wearing traditional concert attire, the musicians also donned Halloween costumes, dressing up as Spider-Man, the Duolingo owl, a butterfly, Vermont Senator Bernie Sanders and the protagonist from the 2019 folk horror film “Midsommar” — to name only a few.