so i found more of irl Holster
which Ngozi herself said sounded like Holster. Since his vine and other social media are all under the username 80Fitz, I had to do some sleuthing, where I came across this article which states:
“You may recognize him as the crazy good beatboxer from Das Sound Machine in Pitch Perfect 2, but make no mistake; 80Fitz has been killing it for a while now. When he’s not making feature lengths films, 80Fitz (whose real name is actually Andrew Fitzpatrick) is making six-second videos on the app Vine — and with a pretty big following, I might add.”
A quick IMDB page search confirms that yes, Andrew Fitzpatrick is indeed in the movie Pitch Perfect 2, in the group Das Sound Machine, who are performing in the first photo posted above.
Now, this dude is fucking talented. His Youtube channel proves that, and he even has a video uploaded that is an extended scene from Pitch Perfect 2 showcasing his talents:
TL;DR: The man who Ngozi said sounds like Holster is prime material for a Samwell Mens Acapella Team AU