The article discusses the unique sounds and melodies produced by subways from different cities around the world. Civil engineer, Ted Green, has collected these sounds from various transit systems for over a decade, highlighting the variety and simplicity of these door chimes. The melody variations, often computer-generated today but sometimes resulting from old mechanical processes, are seen by enthusiasts as a form of audio collecting, capturing the nuances of mass transit systems globally.
What a lovely piece of journo-tech.
https://www.nytimes.com/interactive/2021/08/13/arts/subway-train-sounds.html