The 30s is a glee club consisting of Mayor Macklemore and three other high-school kids who ended up being a doctor, a pilot, and a beekeeper. They used to sing songs every 30 minutes past the hour. When Mayor Macklemore and the other members caught a case of the Sing-alongs, the 30s were reunited to put an end to the singing.
There is a song at the end titled "stop the music" where the four of them have one final performance.