I used to talk a lot about it. I've read a number of books. Authors such as Anthony Frisell define voice type by the bridge point or second passagio. For example, tenors usually bridge by F4.
In an older article in this media site, another equally validated expert of singing defined ranges by taking the lowest possible dynamic sound, regardless of minimal volume and add about 3 to 3.5 octaves to it. By that definition, I am a "high tenor." A classical coach that helped me described me as a light tenor. A friend who is training for opera suggested that if I were to apply to opera training, I might be leggiero tenor. Which are not badges I wear to validate myself.
What is a tenor? Most roles for tenor, at least as I have read, have the main body of melody between C3 and C5. As it so happens, my usable acoustic volume, volume that can be heard above an acoustical instrument or instruments is from C3 and up, nominally to C6, which is the highest note I do in "full voice" or usable acoustic volume.
Which suits me. The largest chunk of music I want to sing falls within those "boundaries." And probably the lowest note I have made, which felt like a croak, to me, is an E2, specifically for the song "Silent Lucidity" by Queensryche. Seeing as it is not opera but "heavy metal," I can get away with it while not being a "baritone." And here is where the variety of opinions from different authors lead me to assume that I can talk about it, like anyone else can (talk about it.)
In more than one treatise, an author has pointed out that before the wagnerian era, there were essentially two male voice types, basso and tenore. And tenors used falsetto. And that word comes from a misconception of what is possible. The idea was that a man could not sing high as a woman without being false, or that his voice was a "false" version of a woman's voice. To me, to be acoustically accurate, falsetto is a state of vibration and resonance (or inhibition, thereof) more than it is a "register."
And I think singers would be helped if they thought of registers as qualities of resonance, rather than varying degrees of thickness of folds and aperture quotients at the glottis. I would refer to my post, Mantra III, rather than re-iterate what is happening in the larynx, though it may be unavoidable.
In the florid bel canto days, lyrics took a secondary role to "legato" or seemless transition from note to note. More often than not, you understood the story in the piece from the published program in your hand than from understanding and hearing clearly defined lyrics. And because of that, low singers could go lower and high singers could go higher because making the word was, though important, slightly behind getting the pitch and making that "lovely."
Along came Wagner, the game-changer, and here is where my amateur theory comes in. Wagner wanted you to hear the song in the singing, rather than have you reading during a performance. The idea is to keep the audience actively engaged in the process of the show. In addition, he was writing "bigger" music. Larger orchestras with larger sounds and playing larger halls, rather than in chambers and even the salons of say, France. This necessitated singers that could recite with clear diction at frequencies more commonly understood by audiences. In short, it brought forth the need for the "baritone." Someone who's strength and brilliance was between the lowest and highest.
And for a while, it was thought that baritones were singers who had simply not trained their low end well enough. But this also leads to confusion because the ranges of baritone and tenor overlap. So, if a baritone is singing notes above G4, does that mean he is now tenor? If a tenor grumbles a note at G2, is he now a baritone?
Because a voice type is not just range of notes, it is a timbral quality, I think.
And here's the kicker. The singer is secondary to the voice type. That is, even in classical training, you are not baritone unless you are training baritone roles and being cast as baritone. Because that is what the music requires. And that depends on what the composer was desiring and more immediately, what the casting director is requiring. And really, these descriptions of voice are only useful in opera.
But let us run with that. Let's say that the general comfortable spot of your voice is analagous with what is commonly perceived as baritone. And you want to sing rock or pop songs that are kind of high in range. So what? Do it. And just because you can does not now mean that you are tenor. Tenor is just a description, not a badge of honor nor should it be a means of validation, whether by self, or others.
So, when it comes to describing a voice in non-classical music, I think it is better to describe where it is centered. I have a high-centered voice, which does not imply range limit. And others have a low-centered voice, which does not imply range limit.
However, I should note that I think there is a bottom limit to a voice, not counting physical malady. Other than the legend (spoken but not heard) of Caruso taking over a basso role for a colleague who suddenly fell ill, I am not aware of an legitimate example of a leggiero tenor now becoming a basso profundo. If some think I am describing a limit there, so be it. But I would like to know of a case of someone who has had a high voice all of his or her life all now able to sing acoustically usable notes in the first octave. Someone may come along with that and I would argue that the singer was a basso to start, who trained tenor roles and then, later, changed back to the low end of the voice he already had. In all likelihood, Caruso had a lower voice that he did not use much since people valued his sound in tenor roles. His friend was sick, so, he dropped down to the lower part of his voice. The show must go on.
Probably the most valuable advice came from the classical coach. Just be a singer. Rather than worry about whether you are this or that kind of singer, just be a singer. I have heard heavy metal singers who are clean. Country singers who rattle. And all shades in between.
Along with that, develope a tough hide. To believe in yourself. Some may not see the value of your voice in a genre. Others will. And it has nothing to do with voice type and everything to do with you and your expression.