From the description

Published on Dec 12, 2012
Top Secret Drum Corps is a precision
drum corps based in Basel, Switzerland. With 25 drummers and colorguard
members, the corps became famous for its demanding six-minute routine
performed at the Edinburgh Tattoo in 2003. With its invitation to
Edinburgh, Top Secret became one of the first non-military, non-British
Commonwealth acts to perform on the Esplanade at Edinburgh Castle.
its success in 2003, Top Secret was invited to return to Edinburgh in
2006 with a new and improved routine. They were invited a third time in
2009 and again in 2012. Under the leadership of Erik Julliard, the band
is also responsible for the founding of the Basel Tattoo, a military
tattoo show similar to the Edinburgh Military Tattoo, now held annually
in Basel.

Oh this is glorious. I have no idea what the source of the name is.