A few times while fsihing last year at night, I heard this troubling sound while drifting, It was very eerie. Sounded like a few violins playing out of tune, very unnatural. One time I moved just to get away from the noise. I thought it may have been some bugs or frogs.
So this year I am out in the morning and hear the same sound, this time I was far from shore.....come to find out, it was the line from the spare rods I have in the rod holders on my T top. the breeze causes the vibrations and produces the violin sound. I took them down since it drives me crazy. Pretty dumb I did not figure it out earlier! :spin:

The rigging on the 70 (the running backstays specifically) I sail on hum at around 7000-8000lbs of load. Drives you batty after a few hours on watch.

Also the keel and rudder over 20 knots start humming.

I was on a friends boat and he freaked out one day.Thought he was losing a pulley on his engine.Sounded like a bearing whine.My rod in the holder had braid that was whining from the wind.I got a good laugh from it.He had the engine cover off,radio down and was puzzled.