For this third sound i used a plastic bottle that i typed in rhythm a table. I applied a dissolve, a development of the basses and changed the height. Then i truncated the silences and made a dissolve in closure.
This was a battery-powered train car running in circles on its plastic track. Is the sound pleasant? no. Did i hold my zoom h4n upside-down in the center of the circuit so the engine slowly pans from ear to ear? absolutely.