[vborovikov]

I discovered a fridge in a supermarket with a very pleasant humming tone. I went there often just to hear it and even tried to record the sound with a shitty mp3-player but it was unsuccessful.

But it was just one genre, music by an artist like Stelladrone or similar.

[kwoff]

A fridge (compressor) in a studio I lived in often made me hear Barber's "Adagio for Strings" (sad song in the game "Homeworld" or the movie "Platoon"). I think it hummed at the frequency of the long note then slowly shifted in pitch similar to the three-note patterns that follow, or something.