We know the voice is a delicate little instrument that can easily be damaged when used incorrectly. Did you know the vocal folds (cords) are composed of three elements: muscle, ligament and an outer fleshy mucous membrane. When used correctly, this little instrument can accomplish amazing feats.
We can’t see the cords while we sing, so it’s important to understand the effort needed elsewhere to ensure the cords are being coordinated correctly for great singing. There are several factors involved: Air flow (which is your breath and involves many other factors to do with your body), position of the larynx, and maximizing your resonance. It is the attention to this balancing act that will allow the cords to stretch out, thin out, stiffen, thicken, lengthen and shorten. The control at the vocal cord level should be the goal of every great singer.
In my opinion, it’s all relative, really.
Here is my definition of falcetto: The condition of the vocal folds whereby the glottis is large and a lot of air is passing through.
Here is my definition of head voice: The condition of the vocal folds whereby the glottis is small(er), and the folds are able to withstand more breath pressure.
Let me explain.
With my own voice, I basically consider my falcetto to be a light head voice. This is the condition where I am allowing more air to pass through on a high pitch.
With some singers, this condition happens when they reach a certain pitch whereby the vocal folds cannot withstand the amount of breath being released. Basically, they blow apart.
In other singers, this condition happens as they gradually get higher and higher in pitch. There may not be an actual sensation of flip, but rather a breathiness that comes with singing high notes.
Ideally we want to have good vocal cord closure on our high notes without over-compression (squeezing). Singing in your falcetto (or your head voice, whatever you decide to call it), is an important element to becoming a better singer.