In a woodwind the sound is generated by the resonating air column within the instrument, the material of construction being of secondary importance. To a first approximation the flute can be considered as a cylindrical tube open at both ends, the clarinet as a cylindrical tube closed at one end and the saxophone, oboe and bassoon as conical tubes closed at one end. All these instruments generate a complete harmonic series and overblow the octave, except for the clarinet which generates predominantly odd harmonics in the low register and overblows the twelfth.