Vowel Formant Structure Predicts Metric Position in Hip-hop Lyrics

In order to be heard over the low-frequency energy of a loud orchestra, opera singers adjust their vocal tracts to increase high-frequency energy around 3,000 Hz (known as a “singer's formant”). In rap music, rhymes often coincide with the beat and thus may be masked by loud, low-frequency percussion events. How do emcees (i.e., rappers) avoid masking of on-beat rhymes? If emcees exploit formant structure, this may be reflected in the distribution of on- and off-beat vowels. To test this prediction, we used a sample of words from the MCFlow rap lyric corpus (Condit-Schultz, 2016). Frequency of occurrence of on- and off-beat words was compared. Each word contained one of eight vowel nuclei; population estimates of each vowel's first and second formant (F1 and F2) frequencies were obtained from an existing source. A bias was observed: vowels with higher F2, which are less likely to be masked by percussion, were favored for on-beat words. Words with lower F2 vowels, which may be masked, were more likely to deviate from the beat. Bias was most evident among rhyming words but persisted for nonrhyming words. These findings imply that emcees use formant structure to implicitly or explicitly target the intelligibility of salient lyric events.

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).