Experimental study of vibraphone pitch bending using electronic speckle-pattern interferometry

Abstract

Pitch bending on the vibraphone is an extended performance technique called for by modern composers dating back to the 1960's. After first striking the middle of a bar with a soft mallet in the normal manner, the pitch bend is obtained by pressing a hard mallet onto the bar at a nodal point and then sliding it away from the node as the note sustains. The audible result is a descending pitch, typically of about one semitone. Experimental data showing frequency vs. location of the hard mallet along the bar are presented and interpreted with the use of time-averaged electronic speckle-pattern interferograms showing the vibrational modes of the vibraphone bar. Frequency vs. mallet mass data are also presented and discussed in terms of a simple mass perturbation model.