Almost sounds dirty.
I use jaw vibrato (on non classical pieces of course). There are several different kinds possible. You might want to try that pink saxohone book as I remember a chapter on vibrato there (don't remember the author but if you've seen it you know what I mean). There's also that machine gun type heard on recordings in the early half of the 20th century - I think it's done by letting the jaw quiver - but don't quote me as I haven't experimented enough to use it. Diaphram (like flutes) may be possible. Since were on the topic, how do you do flutter toungue on clarinet? I can do it on flute where there is nothing stuck in your mouth, but how do you do it with a reed?
how d you do it on flute? by saying rrrrrrrr or using your diaphragm?