This is a video of a saxophonist playing his instrument into the open end of a giant gas pipeline that produces an echo that sounds like he's playing with another musician. Or, who knows, maybe there's another saxophone player trapped at the other end of that pipeline trying to signal for help. Stranger things have happened.
Keep going for the full four minute concert.
Thanks to Richard C, who agrees this is probably a lot cooler than playing a saxophone into the closed end of a gas pipeline.