Spectral envelope consistency singing diatonic scales with different dynamics contours
This study was motivated by the frequently expressed opinion that in the classical style of singing one of the main objectives is the evenness of the voice over wide pitch and dynamic ranges. With an empirical experiment, we aimed to discover whether and how the acoustical parameters related to voice timbre change when professional male vocalists fulfil vocal tasks with changing pitch and dynamics. We asked 11 participants to produce one-octave D-major ascending diatonic scales in three different ways: (1) with their habitual dynamics, (2) with sempre crescendo, and (3) with sempre diminuendo. The values of the corresponding parameters varied systematically in the case of all the singers tested. Some of these changes occurred for purely acoustical reasons that are unrelated to the vocal technique of the singer. Several singers used vocal strategies whose purpose appeared to be the improvement of the perceived evenness of the voice. One such technique was the creation of a difference between the piano and forte dynamics primarily by changing the voice timbre without varying the sound level significantly. An alternative strategy was varying the sound level while minimizing the variation in the level of the singer’s formant (which is related to the brightness and carrying power of the voice).