There are many ways of pronouncing Hebrew in prayers and when reading the Tora. Most of these are tradition-based: one pronounces it the same way his parent or teacher did, or a close approximation. Over the years, of course, the amount of error in those approximations amounts to quite a bit, which presumably explains the wide divergence of pronunciation.
S'faradim, on the other hand, typically pronounce
- a kamatz katan as a fairly closed, back, round vowel, something like o; and
- a kamatz gadol as a fairly open, central, unrounded vowel, something like a.
Now, I've heard some people pronounce even a kamatz katan as a fairly open, central, unrounded vowel, something like a. (Or many a kamatz katan, anyway.) I've always assumed this is not based on the tradition they received from a line of teachers and ancestors: am I right, or is there some tradition that pronounces the vowel this way?