@IRENE 46

Actually, being out of tune is not one of the innate qualities of a voice such as tone is. Intonation is controlled by the brain and by the level of musicianship one has developed. That's why your girl is so often out of tune, 'coz her musicianship is rather mediocre.

So no. Your analogy is completely wrong. Let's put it this way:
- A $100, 000 Steinway piano being played badly; with notes out of tune and banging on the keys in a vulgar and unrefined manner...is simply not good.
On the other hand, a great pianist playing a cheap $50 Casio keyboard with musicianship, refinement, precision, etc...that is MUSIC.

In other words, having a great instrument does not make someone a great singer.
But in any case, in my opinion Christina does not have a great voice. The fact that she can't even belt a decent C5 (a not sitting in the very middle of the voice) shows that her instrument itself is of mediocre quality. And lack of training cannot take all the blame for it, because people like Vanessa Amorosi or Monica Naranjo never had formal training and yet they belt out C6's with ease, support and perfect intonation.