KKW has been posting a ton of videos on her Instagram story throughout Sunday morning which shows Kanye leading a full choir in what appears to be a private studio, as they sing old and new tunes of his, like "Heard 'Em Say," "Father Stretch My Hands," "Lift Yourself," "Reborn" and others.

Interestingly enough ... we didn't hear "Jesus Walks" in any of her posts.

Kim tweeted about the gathering, saying, "Our new Sunday Service is starting. Check out the rehearsals on my Instagram stories." She didn't add much context to what the "Sunday Service" entails or when exactly it's starting ... but it seems they're ramping up for a church venture of some sort.

BTW ... Kid Cudi's in the studio too, as is baby Chicago -- who's big enough now to get her groove on.