Much can change between a movie’s initial trailer and the finished film (like that Anakin Skywalker reference in The Force Awakens). Visual FX will be finalized, scenes may be cut in the editing process to improve the narrative flow, additional footage might be incorporated, and additional dialogue may be recorded. That last one is particularly relevant for X-Men: Apocalypse, as you may have noticed that the titular villain’s voice changed quite a bit between the first trailer and the more recent sneak peeks.

Some fans were less than impressed with Oscar Isaac’s Apocalypse in the early trailer for the new X-Men sequel. Aside from his appearance (which inspired plenty of jokes on Twitter), it seemed odd that such an intimidating, ancient and god-like villain would sound…exactly like Oscar Isaac. But his voice changed in subsequent trailers, morphing into something more booming and inhuman, which some assumed was a direct response to those earlier complaints.

During a visit to the set, Bryan Singer confirmed to IGN that Apocalypse’s voice in the first trailer was indeed Oscar Isaac’s actual voice — but it was never meant to be the villain’s permanent sound:

[The first X-Men: Apocalypse trailer] was simply Oscar using his normal voice — which is wonderful; his performance is fantastic — but that was never the intention. We just needed those words to govern the first teaser. So people thought, ‘Oh, wait, is that going to be his voice during the whole movie?’ It’s like, no, but to tell the story of the first teaser, we needed the voice, and I hadn’t recreated the voice yet.

The director goes on to explain the interesting approach to modifying Isaac’s voice for the finished version of the film, which involved re-recording all of his lines. Additional dialogue recording (or ADR) isn’t uncommon, but this was a special case:

What I’m doing is something very unique. It hasn’t been done before. We’re rerecording his entire performance because the suit’s creaky and makes all kinds of noise, you can’t really use any of it anyway. But I want his performance. So he’s being recorded in ADR using a standard Sennheiser microphone, but also with a bass mic to his right cheek and a bass drum mic to his left cheek. These two microphones have the ability to pull vocal range out of his voice that the human ear cannot hear. And I can take that vocal range that I’ve now recorded, and I can pull it and use it to augment his voice — and that with a little digital magic can create a voice that’s both completely governed by his performance but is not natural.

He also notes that Apocalypse’s voice is dynamic and changes throughout the film to adapt to specific circumstances. Bottom line: this epic villain isn’t going to be speaking with the voice of a mere mortal like Oscar Isaac (no matter how handsome and charming he may be), so if you were worried that ol’ En Sabah Nur over here was going to sound too much like Poe Dameron, you can rest a bit easier.

X-Men: Apocalypse hits theaters on May 27.

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