It’s entirely possible there’s a placebo effect and my experiment actually produced a “false positive” because I subconsciously expected to get vibrato or thought it would be cool to get vibrato and that affected my breath without my realizing it. Or it may be that wiggling something like a leg or foot does affect the breath and produces a breath vibrato indirectly.
This may be the last great frontier of scientific investigation. To infinity, and BEYOND!
Best wishes,
Jerry
Hmmm…I’m not sure Tres. Why don’t YOU try it out…if you don’t bother ever telling us, we’ll have our answer 
On another note, this is all very fascinating to me. As someone who was vocally trained, vibrato from the diaphragm seems to come more naturally. But I find the “flutter” concept intriguing. I think I may have to try it.
Unfortunately, I am a diaphram vibratoist (is that even a word?). My finger vibrato is so lame that I doubt I could get an effective experiment going. Anyone else out there want to volunteer?
Tres
I use “whistle-shaking” vibrato on high whistles, but breath vibrato on low whistles. I also like to use vocal rolls (“diddly”), since my traditional rolls don’t sound anything like a bow triplet yet (but I’m trying). 