Over the past couple of decades in which I've maintained a special focus on intonation I've noticed a peculiar thing about how top professional singers pitch their notes in relation to the accompaniment. I call it "characteristic pitch address" (CPA). Although I've never gotten around to making objective measurements of CPA, time and time again I've spotted CPA happening. And though very subtle I'm pretty sure it's objectively real.
CPA is a more or less consistent but subtle sharpness or flatness a singer maintains with respect to the accompaniment. Luciano Pavarotti, for example, has a flat CPA. Charlotte Church, when she was a young girl, sang with a sharp CPA. But when Charlotte first reached maturity it seemed to me she was struggling with her CPA in a kind of 'identity crisis', perhaps not yet having developed a more mature, flatter CPA to which her audiences might respond with the same enthusiastic adulation as when she was young and sang like a cherubic angel.
I suspect CPA is a largely unconscious marker of 'dominance' or 'submissiveness'. Young girls and boys in religious choirs, with their sharp CPA, tend to encourage the congregation to feel submissive fealty in learning about the ways of the Almighty. The tenors and basses, with their flat CPA, tend to enourage feelings of mature mastery and strong responsibility in facing their known duties to the Almighty. I believe these unconscious effects also translate well - as equivalents - into secular music.
It's a matter of a few cents in pitch - not generally or easily discernible as 'flat' or 'sharp' but nevertheless having an unconscious effect on the listener.
Give it a try in the new Synchron choirs, using the Pitch Cents control in the Editor.
Note that whilst it's pointless having any CPA on an unaccompanied solo voice or section of similar voices - since it's all to do with the subtle relationships between pitches of various different sound sources - CPA cents can nevertheless be applied and left in place permanently.