What does your metro / subway's door chime sound like?

In London they all sound pretty similar, but i'll show them anyway...

Jubilee and Northern lines (1996 and 1995 Stock respectively)

This is a Jubilee line 1996 Stock departing Baker Street southbound:

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Piccadilly line 1973 Stock

A westbound Piccadilly line 1973 Stock arriving and departing South Kensington:

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Central line 1992 Stock

An eastbound Central line 1992 Stock at Perivale:

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District line D Stock

A westbound District line D Stock departing Embankment:

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All the other lines sound more or less like this

A Northbound Victoria line 1967 Stock arriving at Highbury & Islington:

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mic.ro has a whole list plus a few accompanying videos on his site for cities with metro systems. Here's a link directly to the page pertaining to your question (http://http://www.mic-ro.com/metro/announcements.html).