I had a colleague, long gone from this world, who deplored the use of the terms “the singing voice” and “the speaking voice”. Â Many times I heard her in frustration say, “There is only one set of vocal folds. It’s all one mechanism. There is no need ever to say, speaking voice or singing voice, as if they were separate.” I disagreed.
Well, it’s true that we just have one mechanism, but it isn’t so that everything is always the same. For instance, the lyrics are on one side of the brain and music is on the other. There are also differences in function that matter.
Speech generally comes from the thyro-arytenoid function of the vocal folds and singing is often dominated by the upper edges of the folds stretching to higher pitches. The crico-thyroid muscle pulling on the thyroid cartilage takes over. People don’t generally speak in the quality that emerges when those muscles are in charge. There are changes in the shape of the vocal tract (different use of vowels) and the movement of air across the closed and vibrating vocal folds varies according to the pitch, the  volume and the duration of time the sound is being made.
We don’t elongate words to drag the sounds together when we speak (as we do in singing – it’s call legato) and we don’t have vibrato in speech if its normal but we often do when we sing. Conversational speech isn’t very rangy and doesn’t generally get very loud. Singing can be at least four times louder and cover at least twice as many pitches. And, unless you are a baritone, you may not be always singing in the same pitch range or vocal quality as the one you use when you speak. If you are soprano who belts or a baritone who can sing as a counter-tenor, you are straddling speech and song, using both alternatively.
If you are being taught singing is always the same as speech and being told, “Just sing as you speak because that’s all there is”, you have a right to ask: “What kind of speech are you talking about and what kind of singing?” You have a right to tell your instructor, “It’s not so simple as you think. There are some similarities but there are also some significant differences. Let me tell you about them.” Then, read them this blog post and suggest that perhaps they should read some of the various excellent books on singing voice function while you walk out the door without looking back.