Redstone triggering sounds?

Yesterday notch twittered about the possibility that we soon will be able to trigger sounds, or tones with redstone. He gave us this highly illustrative picture.

With C, C# and D being tones. And I can simply guess that the box at the bottom is showing that different materials will give off different sound. And ofc course SP + SMP means that it's gonna work on both singel- and multiplayer. Woho! cool stuff!