I always found Toronto's door chimes to be pretty nice.
London doesn't really have a door chime, just a shrill be-be-be-be-be-beep. However, some of the motors have their own distinctive sounds! The Jubilee line is particularly melodic, emitting a series of harmonic tones as it's Gate-turn-off Thyristor inverters (predating the more modern IGBTs) step up and down through various frequencies as the train changes speed.
Same type of locomotive in front of steel freight, tortured trying to start uphill in the mountains after a red signal, finally manages to after a few minutes. Don't know why, probably had to cool down first?
Disappointed that the article does not mention the very distinct retro-tech drone of the inverter-based power supply of the Soviet Metrovagonmash 81-814 and 81-817 trains (1,2).
Also interesting to note that the Montreal Metro sound lives on as the low-speed pedestrian awareness sound of the electric LionC school bus, which are manufactured in Quebec.
