Hey
I agree to a point in terms of pitch, but it can take training to fix ussues with tonality.
With pitch the singer has a unique problem which causes pitch confusion, making it difficult for the singer to hit the correct pitch. Sound produced by the mouth reaches the ear in two ways:
From the mouth, through the air, to the ear.
From the mouth, through bone (especially the jaw bone), to the ear.
If any of you know any physics, the waves that make up a sound alter when travelling through different mediums. The result? You hear 2 pitches, and the variance can be up to 3 semi-tones!
This is one of the reasons why you sometimes see singers with the fingers of one hand cupped behind their ear, and the heal of their hand towards the mouth. This amplifies the sound coming through the air (just try it). It's also partly why it is recommended to practice singing at performance volume regularly. That' is not the same as full volume.
This helps the singer compensate for the pitch difference, and then eventually through practice rarely if at all need to use it. This is part of "training your ear".
Practice also brings control. At least correct practice does. One of the main problems singers have is breathing. This is very important as you need to have enough breath to make a particular pitch, and hold it.
So most people can with training become reasonable, if not pretty good singers. But some others will never be singers due to lack of concentration, control, or that fundamental feedback mechanism - awareness.
Cheers
John
Cheers
John