Modern professional first-rate bass clarinets commonly have additional keywork to written C3. The bore is cylindrical for most of the tube with an inner bore diameter between 14 and 15. 5 millimetres 0. 55 and 0. 61 in, but there is a subtle hourglass shape, with the thinnest part below the junction among the upper and lower joint. The reduction is 1 to 3 millimetres 0. 039 to 0. 118 in depending on the maker. This hourglass shape, however invisible to the naked eye, helps to accurate the pitch/scale discrepancy between the chalumeau and clarion registers best twelfth. The diameter of the bore affects features corresponding to available harmonics, timbre, and pitch stability how far the player can bend a note in the manner required in jazz and other music. The bell at the base of the clarinet flares out to improve the tone and tuning of the bottom notes.

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