Opera singers are often accused of singing incomprehensible lines of text. Researchers from the Estonian Academy of Music and Theater and Tallinn University of Technology (Taltech) study the underlying causes of this and develop methods to increase the intelligibility of opera.
In classical singing, there are often problems with the intelligibility of sung text, which is however often not the most important part of it, Allan Vurma, professior of the Estonian Academy of Music and Theater, said.
The importance of comprehensibility in classical singing has changed significantly over the ages, he went on to explain. “In the Renaissance singing several lines of text were often layered on top of one other, which made it quite tough to comprehend. Then, in northern Italy, a group of men emerged who were eager to do things differently. They said they want to imitate Ancient Greece where just one person at a time voices their deepest feelings [in singing].”
So the aesthetic beauty and enjoyment of the arias and the intelligibility of the text they sing always represent a kid of compromise. “The beauty of the voice and the abstractness of musical quality are the most important aspects, indeed. But they begin to eat away at each other in an attempt to make the text sung more clear,” Vurma said.
So vocalists, vocal instructors and, lately, musicologists have been working out ways to sing the text in a clearer way.
However, most strategies so far have been based on personal experience, sometimes even contradictory. “Singers look for their own solutions. They can work together, but they are also rivals. It is important to them that it is their voice that is heard clearly,” he said.
“Opera singing is often quite physical, so it is compared to top-level sport,” the professor said.
Analyses of their recordings revealed that, just like in top-level sports, there is always something to improve in operatic singing. Voices that seem to get lost – are not just the listener’s delusion.
The researchers set out to test the hypotheses that in loud operatic singing, compared with speaking, the intensity of voiceless plosives increases less than the intensity of vowels, leading to poorer recognition of plosives.
The study also looked into whether pronouncing the plosive bursts with greater intensity improves their intelligibility in singing.
The acoustic analysis of nine opera arias in Italian from the Classical and Romantic periods performed by 10 classically trained singers showed that the average difference in the intensity of vowels when sung and spoken was 14.6 dB [standard deviation (SD) = 7.2 dB], while the difference in the intensity of voiceless plosive bursts was only 6.6 dB (SD = 6 dB).
In a perception test with 73 participants, increasing the intensity of the plosive bursts generally improved the recognition of plosives in the sung vowel-syllable-vowel compounds, but mainly when reverberation and/or instrumental accompaniments were added.
At the same time, intelligibility of plosives was often better than chance, even when the plosive burst was missing and replaced by silence.
Singing intelligibly is especially a challenge for women. “A high tone means that vowels cannot be sung very distinctly. There are certain ways and tricks to tweak it, but objectively the information in the voice is lost,” Meister said.
Vurma and Meister acknowledged that this can only go so far. “The problem of intelligibility will always be with us while we are listening to opera. It does comes at the cost of no one being able to understand what is being sung at times, but in Aria, bringing out the pure quality of the voice and the music is a priority.”
“Our work tries to explain to vocalist and vocal teachers why exactly the intelligibility is lost in various acoustic contexts,” Meister said.
“Having a better knowledge of the boundaries and the courage to push them allows us to make more informed artistic decisions,” he added.
Vurma and Meister explain to vocalists that in their singing /k/, /p/, and /t/ could be pronounced either more strongly than in speaking or as strongly as usual, depending on specifics of the context in which opera is performed, detailing these specific contexts.
The study is published in The Journal of the Acoustical Society of America.