Natural VOICE Production is not a style of singing! Therefore it does not differentiate between one style of music or another!
Instead it is the one and only true voice that possesses you from within. It is non- imitative, non-fabricated, non-forced and is the most original sound pertaining to one's own personality, character and human identity just like the sound of any acoustic instrument. For instance, a violin cannot imitate a Grand Piano's (nor a trumpet's) characteristic sound , colour or timbre nor can they vice versa.
The Natural Voice's colour and timbre is only achieved via means of bone resonance and NOT muscular effort!
Natural VOCAL Production (slightly different in meaning to Natural VOICE Production) is not a style of singing! Therefore it does not differentiate between one style of music or another!
It refers to the natural bio-mechanics and processes triggered within our body while in the act of vocal phonation (in public Oration or Singing).
The vocalist experiences holistically a coordinated effort of the physical processes and sensations of release and letting go!
It is non-violent, non-held, non-pushed, non-pulled, non-lifted, non-lowered, non-stressing, non-stiffening and non-tensing (ie. avoiding physical rigidity and discomfort).
The end result! One feels as if the body's support mechanism does it for the vocalist without any undue effort as if the individual is floating and gliding on the vibration of his/her own voice
Is truely the only way to sing! The singer's natural voice is unique and original and can therefore sing in all styles including modern pop and traditional classical without the radical vocal difficulty of switching styles.
Notice that any acoustic instrument has its distinct character of colour and timbre and yet is not limited to one style of song. For instance, the acoustic guitar, piano, etc. can only reproduce one timbre particular to its physical properties and yet provided the musician knows the style they are playing in and has the musical knowledge, skill, accent, rhythm, groove and feel for the style and repertoire, the instrument will be able to reproduce the rhythmic, melodic and harmonic effects required of it. THE VOICE behaves in exactly the same way when dispositioned naturally.

"... When one sings "Naturally" one can sing anything and in all styles without any difficulty whatsoever! ... There are no limits! ..." Antonio Maria Lancuba