This video blew my mind: it's a highly-dedicated, very practiced crew of drummers, called the "Top Secret" drum corps, and they are VERY impressive!

From what the video says, these guys are very dedicated.  They come from all walks of life, and have 'regular' day jobs, but devote much of their free time to practicing their 'routine'.

I recommend turning up the speakers and watching in "full screen" mode!

 

 

(Via Youtube)