This is part of a reply I made to someone's question about the process of developing a singing voice good enough to join a band:
So really we are looking at the question 'what makes a singer 'good'?':
Generally I guess it's the ability to make an unfettered sound that comes right out and hits each part of the song just perfectly.
'All' it is, is my old adage 'closed cords in an open throat'. Which of course is so much easier said than done.
To get to that marvellous state we need to: eliminate all habits that tend to distort the throat (including habitual involuntary lanynx rise, altering the vowel along with the pitch and blowing too hard); then we need to understand how to find (and creatively exploit) the fine balance between air and muscle in the cords; develop absolute precision in formation of strongly resonant vowels and develop our understanding of the relationship between vowel shape and the resultant sound.
As you can see above there are two main phases, first the elimination of the old and then the acquisition of the new. In lessons, these two do overlap largely, because many of the development tools we use to eliminate the old are also creating new skills at the same time.
However the true understanding, benefit and use of the new skills cannot actually facilitate a fully fledged singing voice until the throat distorting issues are quite and entirely gone. Singing is a matter of such precision as I have said before while the throat is unstable it is like trying draw a picture on a table that is randomly bumping and jumping around
There's a tendency towards a lack of objectivity, but that is everyone's problem! Objectivity enables us better to practise on our own and thus greatly speeds development by working smart.
And as always with anything skills based, it's about putting in the hours and working smart.