Vibrating an air column generates sound 


    1.1 Free aerophones (41)
        1.1.1 Displacement free aerophones (411)
        1.1.2 Interruptive free aerophones (412)
        1.1.3 Plosive aerophones (413)
    1.2 Non-free aerophones (wind instruments proper) (42)
        1.2.1 Edge-blown aerophones or flutes (421)
        1.2.2 Reed aerophones (422)
        1.2.3 Trumpets (423)
    1.3 Unclassified aerophones (43)
