This is the theme for the area Sorrow Pass from Ori and the Blind Forest, and also plays in the Valley main area. Sorrow Pass is dangerous, spikey and contains the area known as the "dorito caves" (dorito shaped spikes), and also contains the last ability which triggers the music "completing the circle." It is the second to last area. And yes, those are maracas, not castanets. They were as close as I could get with Flat's current instruments. And yes, some parts are empty, but there is no instrument in Flat that sounds like wind.