What is making iTunes stop playing when my computer idles?

I had this happened to me because my audio output was via my HDMI cable, so when the display turned off, so did my audio. One way to fix this is to change your power settings to never turn your display off. Something I'm testing is to see if enabling the iTunes visualizer will prevent the display from going off.

I forgot about this problem; people are still asking about it.

Some time after asking the question the behavior went away. Perhaps it was an iTunes bug, perhaps it was a driver failure. I don't know. I never figured out the cause, so I can't really say what happened. Since it doesn't look like there's any "me too" answers I assume it was something unique. I'd say close the topic but it looks like that's reserved for worse things. Oh well.

Possibly the monitor was connected to the speakers directly. Therefore letting the monitor sleep would also let the speakers sleep.