Not easy to replicate something so nuanced, with timbral variations inside each single note. However, I tried to do something sounding remotely similar (without any presumption of musical achievement) by using Fluffy's Dominus Choir.
Maybe Sonokinetic's Tutti Vox can be used for something similar, but it features just a few syllables, and is more difficult to control (at least for my limited skills).
(In the meantime, I ordered Arrival on Blu-ray. Thank you for this fantastic video).
Paolo
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