I found when I was a child that if I attempt to sing a note in a particular part of my vocal range, I can produce a chord rather than the usual single note. I can even speak in this mode. It is quite difficult to do, as the pitch that I have to aim for is quite specific, has lowered as I matured, and cannot be achieved at all if I have a respiratory infection. It also involves expelling a large volume of air quite quickly, and I can only speak a few words in this mode before having to take a breath, and the amount of air I must expel has only increased as my natural vocal range has lowered.
Does this technique/vocal mode have a name, and is it used in any vocal performances?