What does box music mean?

box music meaning in Urban Dictionary

Box music is a term that refers to what was once known as alternative music back in the 90's. Nirvana, Pearl Jam, etc. The reason why the term evolved was because in college, students would go outside to smoke, these students would sit around the "call box" used to call up to the dorm room for guests to be let in. These "box people" often listened to this genre of music, thus the term.