Lily Pons (1898-1976) astonishes at the age of 76 in the Youtube video below, her coloratura soprano showing little sign of age. Yes, Pon's dramatic singing sounds a bit stiff (towards the end of the clip), but otherwise, if you didn't know her age and wasn't looking, you'd think she wasn't a day over thirty-five. What soprano in her 60's or 70's can exhibit this kind of singing today? I can think of only one: Benita Valente. Her voice was radiant in a masterclass this past year.
Back to Mme. Pons. This may be hard for some to understand, but it is apparent to those who observe the posture of Pon's face and body that she is a great listener. Why? Her face is open, and her head-body relationship exhibits much verticality. This last point is key because verticality, that is, the spine elongating up and down, reveals how the singer is listening. Pons is balanced, unlike Sutherland who could hyperextend and lose clarity of diction in the process. Instead, Pon's poise and balance result in beautiful vowels and diction. The voice is clear.
Can you impose poise/verticality from without? No. You can't make the big muscles of the body make the small muscles of the ear do their job. What brings about verticality and poise? Highly developed self-listening. In the end, it's the only doing.