Modal (or normal or natural or chest) register refers to the natural disposition or manner of actions of the vocal folds. The vast majority of speaking is done in this register – men speak entirely within their chest register, while women speak in both their chest and middle registers. (As a result, some teachers might refer to it as occurring at “speech level”, although female speech inflection also occurs above this register.) It lies above the vocal fry or pulse register (achieved typically by basses or contrabasses) and overlaps with the lower part of the head voice register in males and the middle voice in females. It begins and ends in different places within the human voice, depending on voice category or type, although it can be carried upwards, through the primo passaggio, into the middle (women) or head (men) registers. (This practice is widely considered to be potentially injurious to the vocal instrument.) The placement of the chest register within the individual human voice is one of the key determining factors in identifying voice type.
The timbre of chest voice is warmer and darker (“oscuro”) than that of middle and head voice, and it is characterized by darker vowel qualities or mellowness. Chest voice (voce di petto) is often referred to as the heavy (laryngeal) mechanism because more thick vocal mass – more of the vocal folds - is involved in phonation within this lower register. (The vocal folds are thickest and fattest in the chest register.).
Middle Register and “Zona di Passaggio”
In women, the register between chest voice and head voice is called the middle register, or medium voice. For most women the range of pitches between the primo (first) and secondo (second) passaggi is about an octave. The timbre of this register is generally thought to be a mix of both the chest and the head voice qualities, or an in between colour, giving it a very warm, rich tone that isn’t quite as oscuro (dark) as that of chest voice but also not quite as chiaro (bright) as that of head voice.
The zona di passaggio is the term that is used for the middle voice in men that lies between the primo and secondo passaggi. The range of this register is roughly about a major third or a fourth. As in the female middle voice, it is generally viewed as a mixture or a blending of both chest and head voice tones, although many instructors and singers see the benefit of using mainly head voice tones throughout this range in order to facilitate a smoother, less problematic transition into the head register. (Using purely chest voice in this area of the range produces a shouty, “calling” voice that usually feels strained and requires increased effort.) Ideally, there should be a graduated adjustment or shifting relationships among the muscles involved in pitch change, otherwise known as aggiustamento.
Taken from:Sing Wise