Clarinet toneholes: a study of undercutting and its effects

Greenham, Adrian Clement (2003) Clarinet toneholes: a study of undercutting and its effects. Doctoral thesis, London Metropolitan University.


Clarinets made from the eighteenth century to the present have been examined to determine the degree of undercutting which has been applied to the toneholes. Early clarinets with small toneholes, designed to permit fork fingerings, were routinely undercut to improve the volume and tone quality. However it has been found that as keywork mechanisms allowed toneholes to be enlarged and placed according to acoustic requirements, the practice of undercutting continued.

Good quality Boehm system instruments manufactured today are invariably undercut, but some twentieth-century makers produced professional models in which there was no undercutting.

Experiments have been made in which the acoustic input impedance of specially prepared clarinets with interchangeable toneholes has been measured. The acoustic input impedance spectra showed only small changes in mode alignment as a result of undercutting at low drive levels. Under normal playing conditions, using an artificial mouth to maintain a constant embouchure, it has been demonstrated that undercutting a single hole can shift the frequency ratio between corresponding notes in the lower and upper register closer to 3: 1 (i. e. a musical twelfth). Also, asymmetric upstream undercutting is shown to be an effective method of achieving this change.

The artificial mouth has also been used to explore the inadequacies of fork fingerings in the chalumeau region of the `Classical' clarinet. Also the effects of undercutting, rather than uniformly enlarging the holes, on tuning and timbre has been examined. An experiment was performed, in which eighteen clarinettists were asked to appraise specially prepared clarinets. Three identical cheap clarinets were obtained, none of which was undercut. One was left as a control, one was undercut and the third had all of the sharp edges at the intersections of the toneholes with the bore carefully rounded and smoothed. Whilst the undercut instrument was rated to be of significantly higher quality than the control, a majority of players preferred the smoothed instrument, mainly because of its even playing quality. Subsequently the undercut clarinet was adjusted and re-tested and a selected group of the original testers found it to be marginally better than the smoothed instrument, which they had previously rated as good.

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