Ephemeral oscModulatorNode.

Hi Lonce,

I collected the oscModulatorNode creation code right into the play() function just for illustration. The real design problem is how the sound model should encapsulate the voices that it has to create. The ephemeral nodes of the web audio api expose the voices in the raw, forcing us to think about it, but it is a good design question to think about and clarify as getting it right will help API users.

-Kumar