Evidently the Tokyo rail system uses different chime music to indicate stops so you can subconsciously learn when to get off. Also the BBC provided some brilliant ambient signifiers on their site:

In another case, the BBC’s 2002 redesign of its bbc.co.uk website introduced the wonderfully elegant idea of digital patina (sometimes referred to as “digital color footprint”), in which usage patterns create worn paths (e.g., the more you visit the BBC Sports section, the darker the Sports box on the homepage becomes).

I need to keep this guys concept of the ambient signifier in mind. Where else can this be applied?

I was also sent a pointer to a listing of station jingles for the Yamanote line in Tokyo. Text is Japanese, but I still had a fun time clicking around on the various sound links. This one could easily be the intro for an electronic music track.

Two things need to happen. Someone needs to construct an entire ambient album based mostly on these samples. And, I need to find a way to slip these into the BART system.