Found it:
"George’s portrayal of Vina didn’t just require building on the arc the character went through in 'The Cage' — it required going back to the pilot in a more literal sense too, apparently, even recording over lines of Oliver’s original dialogue so 'Discovery' could blend the two voices together for some moments, connecting the same character despite the half-century between performances...
"'They did put some of my voice on top of hers to kind of meld the two together. I couldn’t recreate her acting because so much has changed the way we act today. There’s a different kind of inflection. But I wanted to watch it and pay homage to her and the way the character felt....'"
Last night’s fantastic episode of Star Trek: Discovery had a bunch going on—but one of the most fan-pleasing events was a trip back to where Star Trek
gizmodo.com