Joerg, I think I should listen to some example of what you want. There are so many things we still don't know, that it is possible we completely overlooked (overheard?) some singing style. I remember my impression when I first heard a chinese singer, or the incredible harmonies of South African spirituals. I still owe to myself to listen to an Indian singer with their three-octave range, and who knows what else.
My example of Shakira (she is a Colombian pop singer, now fidancée of Mr. De la Rua Jr., son of Argentine President) is the most dramatic example of NOT respecting the melody: her voice mantains the tune 90% of the time, and the other 10% abruptly breaks to a nasal sound three or four tones above, giving the impression of "jumps" in the tune, or, of a person who wants, but CANNOT sing a simple, popular and occidental melody. However, she is famous and successful, and I am only famous.:))
Un abrazo - Andrés