for classical singing u need to sing with ur diaphgrm supporting it. it goes for all form of singing if u want your voice to sound clear and articulate .
e.g Bon Jovi , living on a prayer --> bon jovi has pretty decent technique
but like led zeppelin (dun flame me for this , i am a led zeppelin fan too) , robert plant , if u seen some of his lives , his voice cracks and wavers when he sings. thats bad technique.