Our sharp-eyed users (you know who you are) will undoubtedly notice this, so here's the official story:
After about five years on active duty, we are retiring our old Genre listing Ambient/Trance/Techno in favor of the simpler and more accurate Ambient/Downtempo. All the tables and menus in both the RADIO and ALBUMS sections have been updated to reflect this.
While there was some wiggle room in the meaning of these terms in 2001, at this point Techno generally refers to an established category of electronic dance music, and so does Trance. While the term "trance" can also describe spacey psychoacoustic electronic music, we already had a category for that: Electronic Space.
Ambient remains a bit of a catch-all term, and seems to be serving its purpose in the taxonomy of atmospheric music — namely, contemporary atmospheric/electronic music that is not organized around new age ideas and images, even if it sounds virtually identical. Thank you, Brian Eno, we're stickin' with it.
In cases that are ambiguous, we will simply assign the album, track or program to multiple genres, including our own "catch-all" — Contemporary Instrumental.