The ebullient tenor recalls his "first go" as Otello in 2009, in concert with the London Symphony Orchestra under Sir Colin Davis.
"When I got into the Barbican the whole room was covered with microphones," O'Neill remembers. "This was my first time in the role and it could have been a fantastic operatic suicide in public."
However, it turned out well, he admits, as did the ensuing CD. Five years later, in the Sydney Opera House, he scored another triumph, with Nicholas Routley of Australian Stage confessing that he had "rarely heard such a convincing fusion of great singing and total character portrayal."
And what else would one expect for what O'Neill describes as one of the most amazing characters in opera, based on the supreme Shakespearian anti-hero.
"Vocally it suits me, and singing Italian gives me the chance to pour some olive oil on my vocal cords after all those Mercedes Benz roles in Wagner," he laughs.
The challenge is to catch "the crumbling of Otello's character in your singing, without sacrificing beautiful tone, power or authority." He singles out his great Act III aria, in which he asks God why he has been afflicted with a seemingly unfaithful wife, a piece which, for some minutes is based on just one note.
"Some famous tenors have interpreted this very dramatically, almost moving into speech-song," O'Neill adds. "I love staying on the notes, holding them against the surrounding dissonance. Sir Colin Davis certainly liked that approach, as did Riccardo Muti when I worked with him."
O'Neill has no problems with Friday's performance being in concert rather fully staged, assuring me that there will be absolutely no lessening of his dramatic involvement.
"There was no staging when Christine Goerke and I did our Wagner Gala last year. Even without swords, breastplates and a ring, it still thrilled the audience.
"Otello in an opera of conversations," he muses. "Between Otello and Desdemona and, above all, that great one between Otello and Iago where you see the poison being poured, drop by drop.
"You don't need staging to make this work, just musicians who are willing to listen to each other. It's not only a matter of singing, but also one of listening to other people singing and reacting to them. That's what opera's all about."
What: Auckland Philharmonia Concert, Opera in Concert: Otello
Where & when, Auckland Town Hall, tonight at 7.30pm