The rehearsal space for drum group Tokyo Dageki Dan seems more like a football locker room than a spot to experience one of the country's most honored musical traditions.

Seven drummers joke around while prepping their wadaiko, Japanese drums that can measure anywhere from 30 cm to a meter in diameter. Once practice starts, though, the joking ends and the "athletes" focus; their soft voices become booming yelps that compete with the thunderous sound of the drumming. You've got to be strong to play drums this size, and many of the members play sports to gain the stamina needed.

Tokyo Dageki Dan (whose name loosely translates as "Tokyo Attack Group") is made up of seven main drummers and a few trainees. This year marks the group's 20th anniversary and over the past few years the men have managed to bring their take on a Japanese tradition to the attention of new generations of fans.