Yeah, ya never know what's going to get people's curiosity.
When I first started singing black gospel regularly, with a Men's Chorus I found that all rules for singing were off. When you're singing in a group of 40 men, most of them with powerful voices, singing at full throttle, you have to reach down inside yourself. I have no idea what I mean, technically or physically, but I discovered that there was a new dimension to my voice. It was like a new toy.
In singing, I've gone on a Cook's Tour of singing styles in my life. In High School, I wanted to sound like Frank Sinatra, and had his phrasing as down pat as the average Japanese teenager. When I started hearing Clancy Hayes singing with Bob Scobey's Frisco Band, I had a new idol... much more blues/folk in timbre. He fit in just fine with singers like Gene Vincent and the rockabilly singers I loved so much. When I first started hearing traditional music, I tried my hardest to sound like some old, toothless hillbilly sitting out on the back porch with a banjo. Vibratto was nothing but pretension, as far as I was concerned. I wanted to sound more like a car tire that was just stabbed with an ince pick. It took me years to get over the Zero-vibrato style of singing, and to just relax and sing in whatever my "natural" voice was. Through time, I became more comfortable singing more like I did back when I was trying to be Bob Scobey. Even though I sang black gospel, and some blues, I sounded pretty much like an ageing white kid from southern Wisconsin.
All that finally changed when I started singing black gospel surrounded by black men. I'd never tried to imitate anyone, and consciously, I was just trying to be heard. But, through time, my whole style of singing changed subtly. It's not that I sound like Louis Armstrong now. But we are all the summation of our experiences, and like you, singing where I really have to drive my voice, where there is a lot of rhythmic freedom has changed me.
At least the way I hear myself.
I'm sure there are all sorts of technical explanations for all of this, and there are many Catters who are far more sophisticated technically than I am. They can explain it a lot better. Mostly, I guess I became more of a chest singer than a head singer..