Rare is the show that features more than 750 performing musicians. Such a once-in-a-blue-moon occurrence happens at Midlothian High School on Saturday, Oct. 4, when the school holds its annual showcase of regional high-school marching bands. Featuring the big, bold and brassy sounds of student groups from Atlee, Glen Allen, J.R. Tucker, Mills E. Godwin, Park View, Warwick, Cosby, Meadowbrook, Matoaca, Monacan, Manchester and Midlothian high schools, the day of acoustic heavy metal competitions ends with a panel of judges issuing awards based on the groups’ high-stepping performances. The melodic blowing, beating and syncopations come together at the only marching band competition held in Chesterfield County beginning at 5 p.m. Admission is $7. midloband.org.