Ok, this may have to do with your cpu config and your plug-ins. Since I'm assuming you're using mp3's, it seems that maybe your cpu is not able to handle all this. Correct me if I'm wrong, however.
Since you did say that you were using the OST mp3's, I would suggest something else. There's a beautiful file format that someone created called the .PSF. What it does is take music ripped directly from the game, and is easily playable. Someone has managed to rip the full FF7 OST into PSF format (except for some minor songs). I would greatly suggest using the PSF's over MP3's. Why?
1. PSF's can loop by themselves effortlessly
2. PSF's are so much smaller than MP3's (less resources required, I believe)
However, if you're not interested in using PSF's that's okay. If you still wish to use the mp3's, I will guide you through using them. Just tell us your specs, and we can guide you through this..