>When one of my user apps is running, it seems to somehow interfere
>with the player's ability to spin down the hard drives.

That happens because the player itself likes to control drive spin up/down, rather than leaving it to the operating system. That works very well, so long as the player is the only app running..

In your case, I bet if you don't touch any controls until after the next time the player reads a new track, the drive will then spin down.. kinda not too useful to you, though.

This here will fix it for both you and the player: hdparm -S1 /dev/hda

Cheers

-ml