The great New Zealand comedy duo Flight Of The Conchords — the self-proclaimed “fourth most popular folk duo in New Zealand,” although you’d think they’d be at least the third most popular by now? — have a new HBO special, Flight Of The Conchords: Live At The London Apollo, coming up. They went on The Late Show With Stephen Colbert last night to promote it, where they talked about aging, fame, and the Prime Minister of New Zealand’s upcoming visit to the show before heading over to the stage to play a new song.

“Father And Son” isn’t exactly new, as Bret McKenzie and Jemaine Clement have been playing it together for a few years now. But it’s never been properly released, and it serves as the opener on their upcoming HBO special, which was recorded live at the Eventim Apollo during their UK tour earlier this year and airs on 10/6. The song finds a father (Clement) and son (McKenzie) singing a duet about their love for each other that somehow turns into a song about the boy’s mom leaving his dad for another man named Trevor. (What is it with Oceanians and Trevor?) Watch below.