Masking Effects in Practical Instrumentation and Orchestration

Abstract

The relationship of one instrument to another within an ensemble and the quality of the composite tone produced have been empirically explored by the great composers of the past. Trial and error have played an important role here, however, and the reasons for the existence of intra- and inter-instrumental relationships within an ensemble which influence the tonal sensation have never been investigated. The effects of masking in the tone quality of one instrument in the presence of others are herein considered. The strong partials of one instrument influence other partials in the composite tone of that instrument as well as the partials comprising the combined tones of the other instruments. For illustration, an ensemble consisting of a cornet, French horn, trombone, baritone and E♭ tuba were selected to present a simple chord in varying settings and degrees of dynamics. The hypothesis is that masking in ensemble-playing consists of an accumulation of the masking effects produced by the components of the complex tones. The phono-photographic measurements obtained by Seashore and his associates were used to plot the strength and distribution of the partials within the tones produced by the various instruments. Total average pressures exerted by these instruments were adapted from the data given by Sivian, Dunn and White. The average reference intensity level of 40 db was used to signify a medium or mezzoforte tone level, and a sensation level of 20 db and 60 db were chosen for piano and forte tone levels, respectively, with resultant variation in the partial strength of each instrument in the spectral analysis. These results indicate that chords do not sound as they are written, and substantiate our hypothesis in that conductors alter the intensity which the composer has assigned to various instruments in combination to produce desirable effects. In many instances the notes of the chord must be reassigned to different instruments in order to secure good balance. Definite principles for the guidance of instrumental composition can thus be set up.