Singing through a narrow mouth shape focuses the sound.
The way I’ve had success with this has been to work with imagery rather than with approaching it from the physical side.
Positioning the mouth, then holding it there isn’t nearly as effective as creating a visual image – which produces a more relaxed and subtle shift.
But creating an image without really even using the conscious mind seems to work best of all. This is where kinaesthetic tricks come in handy.
The Peter Pointer Guardrails help to keep vocal placement on the right road – narrow and forward.
Peter Pointer Guardrails = Both index fingers pointing straight up and placed lightly (no pressure) on either side of the mouth.
The sound is more focused because the singers’ minds are now filled with the image
of singing through a more narrow shape.
If still more focus and projection is needed, move the Guardrails out to arm’s length, where instead of Guardrails, they become more like Goal Posts.