When I’m determining the voice type of a student, I operate under the assumption that the size and shape of your instrument (i.e. larynx and vocal tract) truly determines the type of voice you have. The size and density of your vocal folds and the size and shape of your vocal tract will determine whether you are, say, a violin or viola vocally-speaking.
Most people think your vocal range determines your voice type. The problem with this is that many people have not been trained well enough to really know what their range is. Your potential range, in addition to timbre/color and flexibility, truly determines your voice type. In a first lesson I generally will have a student slide slowly through his or her range on vowels or lip buzzes and listen for what are called “passagi.” These are the pitches where your instrument wants to switch between chest, middle, and head voice. I then rely on a sort of mélange of the Fuch system, Richard Miller’s writings on training the soprano voice, and my own experience to determine what kind of soprano you may be.
So, what’s up with sopranos, and why would you want to know what type of soprano you are? The greatest advantage in determining this, I think, is the ability to sift through repertoire. There are so many kinds of soprano that it’s pretty easy to find and sing songs that don’t actually let your voice shine. An experienced teacher will be able to determine your voice type and then direct you toward pieces and roles that best suit you.
Passagi can be tricky to determine in a soprano because the actual passagio may not line up with the pitches on a keyboard (it could be on either the high or low end of the F#, for example). That said, however, here’s my simplified list of sopranos and what I generally look for when classifying a voice for repertoire purposes based on my teaching experience:
After all is said and done, your passagi may not fall exactly into one of the ranges I’ve described. You may be more flexible, and able to play different types of roles. Maybe you’re just awesome like Anna Netrebko and you can go from singing Norina in Don Pasquale (coloratura soprano) to Lady Macbeth in Verdi’s Macbeth (dramatic soprano). Often a director’s vision will influence the voice type that fills a role. I’ve been in several Gilbert and Sullivan productions. Some were headed by musical theater directors and some were led by opera directors. The opera directors tend to cast me in soubrette or coloratura soprano roles, while the musical theater directors will cast me in a dramatic soprano or mezzo role simply based on my vocal weight compared to the other singers in the production. However, I still think it’s useful to know what type of soprano you are so that the pieces you choose to audition with reveal your strengths.