We’ve got our set of three feathers on one side, three feathers on the other side, one of them is kinked and lies over the one next to it. As the wings oscillate and the bird is knocking its feathers together, that pick feather, the one with the kinked end, gets slid over its neighbor over and over again, and as it slides over, the pick slides over the washboard, and it turns out there are seven ridges on that washboard. So if you slide over seven ridges on the way in, and seven ridges on the way out, and do that over and over and over and over again for every knock, you go from that 107 beats a second to that 1500 beats a second. [107 x 14 = 1498] You go from something that’s happening at one speed to something that’s happening at the speed that we actually hear the sound at, and so boom, all of a sudden we’ve got this explanation for how this bird is making sound.

End of transcript

It turns out that as the Club-winged Manakin’s wings come together, each specialized pick feather slides over seven ridges on the adjacent comb feather. Next, the wings spread apart, and the picks slide back into place, passing over the same seven ridges a second time. Thus, for each wing-knock, the pick feathers “pluck” that enlarged (fat) rachis 14 times. 107 knocks per second with 14 “stridulation beats” for each knock produces a vibration in the feather shaft that makes the sound that we hear—a sound of approximately 1,500 beats per second (107 knocks/sec. x 14 stridulation beats/knock = 1,498 beats per second).