I expect there are some dopers who are highly educated in this sort of thing. Rare indeed is the subject with which no doper is familiar!
When a singer or musician uses vibrato, i.e. variation in the pitch of the note he/she is either singing or playing, does the pitch vary above or below the fundamental note? Or, as I suspect, could it be either way?
I ask this because I am trying to sort out the design of an electronic instrument that can sense the pitch of a note being played/sung in real time (i.e. this is not a “tuning device,” but a performance or ear training aid). When we listen to a note with vibrato, our brains have no trouble figuring out what the note is supposed to be, even though its instantaneous pitch is varying all over the place. Computers are notoriously bad at that sort of thing, however. Hence, this will be quite a challenge. I would like to know how our brains “know” what the note would be sans vibrato. How the heck do we know whether the singer is flat when her instantaneous pitch actually is flat due to vibrato?
Any information on the precise mechanics of vibrato will be most helpful. For example, stuff like, what is the range of frequency or variation (probably ranges from about just under 1Hz to “Stevie Nicks”), what is the range of frequency shift (probably about a semitone, give or take a few cents, I would guess, but with pretty wide variation between individuals), that sort of thing.
And anyone who understands a bit about the psychoacoustics of it all–how our brains process this stuff and sort out whether a performer is on pitch–would be the most valuable of all to me.