Powering Down / Descending Sound and Others

Just the other night, I heard a sound that I had heard several times since I've lived in this area. I've heard natural sounds like coyotes, owls, crows but there have been a few sounds that have perplexed me as far as what they are and where they could be coming from and what could be making them.

The first sound is a descending or "powering down" sound that starts at a higher pitch and ends low. The only thing that I have ever heard that sounds similar to this is the NOAA recordings of sounds underwater that are unknown. There is one that sounds very similar to this but in their case it is underwater and in mine, I'm not sure if it is in the air, on land or underground. It is quite loud but I'm not sure as to its proximity as I never see anything when I get up to look out of my window. It always occurs deep in the night (3-4 am) and I'm usually awakened by it.

To me, it sounds like a huge machine being powered down although I can't think of anything close by that would fit that description. There are factories and even a railway but those are quite far and the only reason I know they are there is that I see the steam coming out of them during the day and have been stopped by the train passing through that area as it goes by.

The second sound I heard and this was back when I first moved into this area and there were far less houses here then, was also late at night and I had awakened to a sound like a crowd cheering similar to a football stadium. I thought maybe I left the TV on but it was off right in front of me. I could tell the sound was traveling as it was changing as it came closer sounding more like screams from people that were in pain. It lasted less than a minute but it made me stay still listening well after it departed.

Last one was also recent and was on a windy day, I heard at first what sounded like a flute/recorder playing at night. I couldn't recognize the tune but it was definitely music and not just random notes or just noise. After some time, it sounded like it changed to an organ which makes absolutely no sense as there isn't a church or anyone (that I know of) that has an organ in their home that loud. Finally, it changed again to something like bells which makes more sense as I've heard my neighbor's windchimes but this actually sounded different.

It hasn't but I wish I could find an answer.