A poor singer has lack of multiple resonances in the voice, a lack of vocal control and awareness, a lack of musicality and rhythm, and cannot reliably sing a note on pitch.
A good singer has excellent breath control. He or she uses all the core of the body and all the resonance chambers, from pelvic floor and abdominal muscles, through diaphragm and lungs, to larynx and sinuses. The voice can shift at will from deep, through bell to nasal, soft to loud, or projected to localised. He/she can annunciate clearly so the listener can hear every word. She/he can alter the vowels to produce cords - as in Tuvan throat singing. Practice develops the muscles so that the normal speaking voice becomes incredibly rich.
This post was edited by Benedict Arnold at April 29, 2018 9:44 PM MDT