great video links. I had an experience this last summer where there was a massive tree fallings or rock falling sound but the weird part was it lasted much longer than a tree fall would last and there wasn't much of a difference between the start of the sound and the end part, where you would generally expect to hear a fall off in sound levels. It was quite interesting. I just laid still in my tent and I waited and was not disappointed. 10 minutes later I heard a 4 tone singing like sound like it was being played over a concert speaker. The song/call lasted more than 30 seconds. As I reflect on it, it was beautiful and it sounded like something was singing me a song. Video #4 has some very similar sounds in it to what I heard. Its nice to find a reference point. Thank you for sharing these.