Here's a bit of science and history for you:
(Everything you need to know about Mix.)
For any stringed instrument to function efficiently, (i.e. piano, volin, the human voice, etc.), two elements must be present: 1- the vibration of the string creating the pitch, and 2 - the resonance of the instrument. Say it again: 1- the vibration of the string creating the pitch (vocal cords) and 2- the resonance of the instrument (your body). Now think about that for a moment.
Both of these elements (vibration and resonance), were given equal importance in the original and pure bel canto singing methodology. However, in the late 19th century there was a split within the bel canto world.
One group continued on as bel canto, focusing more on the resonant portion of the technique and the feeling of the resonance behind the soft palate. (operatic stylings)
The other group focused more on the vibration portion of the technique, calling itself “forward singing.” (broadway/pop/rock "belt")
By mixing the chest and head voice you receive the full benefits of “both voices”:
the natural and powerful sound of the chest voice (belt)
and the beauty and range of the head voice. (bel canto)
Learning to balance the air and muscle required to make sound will allow you to experience this mix.
No “breaks” in the voice.
The “break” also known as "passagio" (passage) is a common complaint among vocalists.
When you MIX, you eliminate the break in your voice.
In fact, when you mix, you are experiencing:
a sound that is natural and unaffected.....
a sound which soars through the entire vocal range, connected, from the deep to the sublime.....
a sound that can be used in ANY STYLE of singing......