How the audio is played is interesting:
You’re reading that right. That’s a HTML5
<audio/> tag. First time I’ve seen it appear in a major product. However as of this writing in Firefox, Safari, and Chrome on Mac OS X the Flash player seems to be used. I suspect, but can’t confirm that this may indicate a future intent of using HTML5
<audio/> in place of Flash. Flash is likely the default for now. But it’s still very interesting to see.
The audio itself seems to be 44,100 Hz 320 kb/s MPEG Layer 3 (MP3) audio. The samples I’ve looked at were encoded with LAME 3.98.2. Obviously if they intend to use HTML5 audio they will need to offer something other than MP3 at least for Firefox users. It’s not currently possible to serve everyone without multiple encodings. I don’t see that changing anytime soon.
The servers serving the media seem very similar to YouTube’s delivery servers for H.264 video. It’s progressive download, again just like YouTube. No DRM. I suspect there’s a shared history between this delivery system and YouTube or a very strong influence. But knowing how Google works, there’s likely a shared backend.
It’s pretty good stuff. I highly recommend checking it out. Google built a decent mp3 player in the cloud.