I’m interested in doing real-time analysis on vocals in order to rate how "in tune" they are, using a programming language called Max/MSP, which I've been working with for a couple of years now. Something that’s sophisticated enough to be able to point out when the singer hits a wrong note. I'm on this forum to address a more basic question before I can begin and that's how exactly to quantify "when the singer hits a wrong note". How would a singing professional, like a vocal coach, define a missed note? I'm talking as far as pitch only, not tempo or anything. It may seem like an obvious question, but it's really not. There are plenty of programs out there already that detect pitch and perhaps compare it to a reference melody in a karaoke sort of fashion, but that’s not exactly what I’m asking. My question is: how does one take completely freeform input and decide if there are mistakes in it? As a test, I thought I could use a clip of some a cappella singing, something professional that definitely doesn’t have any off notes. However when I run my pitch tracking analysis on it, it seems that the singer spends an equal amount of time in the gray area between pitches as near or directly on them. I suppose this is because the singer’s voice slides all over the place and rarely stays completely stationary for long. So what exactly makes a note sound bad, when a skilled singer is using vibrato and sliding through all sorts of off key pitches all the time anyway? My hypothesis is that it’s the moments that the pitch does stay stationary that count; the mind doesn’t really pin anything down as being on or off key as long as it keeps moving. Kind of like how you can vibrato your way out of a shaky landing at a pitch and still make it sound alright. Is this a sound assumption to make? Any other insights into these questions?