As one moves up and down the scale, or steps up and down the steps, the vocal cords are being adjusted by the closer and stretcher muscles. This means that for each and every pitch there is a specific length, width, and depth of the vocal cords vibrating.
Not only that, but the brain also sends info to the cords as we think of the vowel to sing. The cords shape themselves for that vowel, and transmit that info to the oro-pharynx where shaping occurs as a result.
Voila! A vowel is formed. Of course, this is assuming that all is well.
If there are issues with how one thinks, feels, or hears the vowel, and with how one has learned to shape the vowel, then there may need to be correction.
But, if there is healthy development and adjustments of the vocal cords for the pitch, and we have healthy adjustments for the vowel both at the level of the cords and oro-pharynx, then we will feel the “step” as correct for the area with tiny adjustments everywhere. The vowel will correspond to that step in size with a certain shape.
For example, an [ah] is an [ah] wherever we go in the vocal home. Yet, notice that as we step up, step by step, the vowel changes in its size and shape. When we sing an upper note, the [ah] will feel like it is smaller and more compact in order to stand on the smaller step. There will also be a feel of the vowel being back and up, according to our upper note step. Further, we have a sense that the vowel is a bit rounded as if it were to move from the [ah] as in “father” to the [ah] as in “sorry.”
This process is not something we should overly focus on or try to make happen with our mouth. As the voice works better, this process will happen as a result of commands given by the registration. The vowel should take care of itself.
After we have this experience of a feeling that is correct, where the vowel is the right size and shape for the specific pitch, then we notice the feel and we remember the feel. With consistent repetition of the correct feel, we have muscle and mental memory wherein we trust our cords and oro-pharynx will respond super quick to our thought; adjusting for pitch and vowel.
We will have voweled tone that is on pitch, beautiful and recognizable!