I only started singing soul music well when I started keeping a large horizontal embouchure and I started pushing the back of my tongue up and the soft palate down, sounding more "nasal". This creates a soulful/squeezed sound that is great when I sing Otis Redding, John Belushi, Wilson Pickett, James Brown, The Doors, Stevie Wonder and so on... Is that the right mouth configuration for that style of singing?
Unfortunately, I cannot find a teacher that seems to agree. One coach, recently told me to try to sing with a more neutral mouth and a lowered jaw, rather than an American large configuration of the mouth. His intention was to reduce the tension, but in the end he also realised I cannot have that same nice soulful sound if I sing in that way, and it sounds more like Pavarotti singing rock n roll.
Other times I was told to keep the tongue neutral and raise my soft palate. That also doesn't work well when I listen back to my recordings.
Is there any standard way of singing for soul singers? any standard mouth configuration or embouchure?