Examining the singing voice as a musical instrument we see that, like any other, it has a recognisable structure of interrelated parts. Take a part or two away, or neglect them, and it will no longer play as easily as it did when it was whole. The more parts fail to work, or to work fully, the less recognisable the singing voice is as the instrument it was supposed to be.

Harrison, Peter T. Singing: Personal and Performance Values in Training. Dunedin Academic Press, 2014.