Without responding point by point, I think terminology is being mixed up a bit here.
A. Windows Power Management can;
1. Sleep the PC after a set period
2. Hibernate the PC after a set period
3. Turn off the Display after a set period. (As long as the monitor accepts power down commands, which most do these days. I know previous versions of Windows also had the ability to blank the Display if it didn't accept power down commands. I assume Windows 7/8 still does this.)
B. Your Display / Monitor / TV can (depending on hardware);
1. "Sleep" the display (blank the display, or in the case of some Plasma screens, turn the brightness way down)
2. Turn off, going into a Standby state.
Some hardware allows timeout intervals to be set, many don't.
C. A Windows or Third Party screensaver can;
Activate after a certain period of inactivity with no input from the user. A screensaver will display some moving image on the screen until there is user activity again.
Note that some hardware people talk about their product's screen saver capabilities, which I think fall into category B above.
Initially this thread, I thought, was talking about category C. Specifically, the Windows screensaver. But I guess the discussion about powercfg means everyone is thinking category A3. The "Disable display from turning off" setting would apply to category A3 I believe, and possibly prevent the category B functionality from activating?
So, to address the OP. If what is wanted is a screensaver that activates while music is playing, wouldn't the Windows or a Third Party screensaver as per category C do the job? Of course, it may activate when a movie is playing and there is no user input. Or does MC control the category C screensaver as well as the category A3 capability?
Heh, I probably just confused everybody. Sorry about that. But I've had my share of mixing up the different screen saver capabilities in PCs, so I thought I would seek to expand the discussion, or focus it just on one area.