I've only been to 2 concerts in my life, one when I was a little mildly HoH, Spice Girls-obsessed 9-year-old.
The second was a Rajaton concert last year. If you haven't heard of them before, they're a Finnish a capella group of 6 (3 men, 3 women, ie. bass, btone, tenor, alto, mezzo-sop, sop)...