This is a video of a man dropping a screw through a turbine engine. It sounds beautiful, but it's a sound no turbine engine technician wants to hear "because it means you have to get that thing you dropped in there back out. Jet engines are heavy and sensitive, so it's a big deal to lift one up and turn it over, just to hopefully drop out a small piece that some dumbass dropped in there. If that does not work, the engine must be disassembled to the point where the item can be retrieved. This will be an expensive process.... that's why it's a bad sound." Yeah, well *jingling pocketful of screws and pennies* I'm no jet engine repairman and I think it sounds pretty.
Keep going for the video.
Thanks to hairless, who agrees the real sound you don't want to hear is a screw passing through a jet engine when it's running.