Vibrating a membrane creates sound. 1.1 Struck membranophones (21) 1.1.1 Directly struck membranophones (211) 1.1.2 Shaken membranophones (212) 1.2 Plucked membranophones (22) 1.3 Friction membranophones (23) 1.3.1 Friction drums with stick (231) 1.3.2 Friction drum with cord (232) 1.3.3 Hand friction drums (233) 1.4 Singing membranes (kazoos) (24) 1.4.1 Free kazoos (241) 1.4.2 Tube or vessel kazoos (242) 1.5 Unclassified membranophones (25)