We do not have plans to add background music support to G3. I can appreciate the fact that you miss it, but frankly there are so many free players available that do it better, we didn't see the point. In G2, you could enable/disable individual songs from a list, but that was awkward (especially if you had a lot of songs), and that was all the control you had--no pause, FF/RW, or skip-to-the-next song (or previous song) functionality.
To really do it right, we would want to add all of those things, and probably more, at which point you're probably also talking about adding a whole new gadget to the sim. That kind of new feature would require lot of time and effort. Rather than turn RealFlight into a fancy jukebox, we looked around at the existing music players available elsewhere and decided our users would be better served by us focusing our efforts on the other aspects of the sim--features which aren't readily available elsewhere.
That's not to say it won't ever happen. We're still open to it if enough people feel strongly about it. I'm just trying to show a little of what went into the decision we made, and why--based on the feedback we've received so far--it's unlikely we will add this feature.
Your point about performance is well taken. However, I would expect other music player apps to perform much better and demand fewer resources than Windows Media Player. I personally use the free version of
Winamp. Now, I run an older version (2.80) instead of the latest available (5), so I can't speak for the current version, but on my system Winamp takes 0% of the CPU most of the time it's running, and occasionally spikes very briefly to 2%. This has no discernible effect on G3's performance. Another option might be to disable the visualizations in Windows Media Player. I haven't experimented much with their player or even paid attention to its performance, so I'm afraid I can't offer much help there.