The song, Baba Yetu, won a Grammy a few years back, and its composer Christopher Tin actually helped the pair out with their pronunciation in this clip.
Blowing my mind, though, is the fact that Hollens also pointed us towards an English translation of the song. Turns out the lyrics to Baba Yetu are the words to The Lord's Prayer, only in Swahili. All this time, and I'd never bothered to look that up. Turns out nobody else here had either. Minds, blown.
So if you've been singing along all these years, blissfully unaware to what you were actually saying every time you blasted out "BABA YETU" (Our Father), now you know.