In a video broadcast interview with Breakfast Television Toronto, Adam Met confirmed the existence of an “Overture” track in the same fashion as the previous ones for Living Room and The Click. (Quote begins at timestamp 2:41.):

[…] we grew up in New York City. So, theatre has always been a part of what we do, and we are so inspired by the story-telling aspect of theatre. A lot of our albums have overtures on it, and that’s also really inspired by theatre. [It’s] where people [perform a] little bit of the song before they dive into the album. This new album OK ORCHESTRA does have an overture on it.

However, “OK Overture” strays from its predecessors in the amount of its original content. While the bulk of the song is a traditional overture, AJR intentionally added the new content, which was confirmed via Twitter.

We wanted to welcome everyone into the world of [OK Orchestra] so it needed it’s own little story about the sad orchestra