The HS50M are monitor speakers, right? Did you connect them directly to the Fast Track Pro? That won't work - you need a amplifier to power the speakers. The interface only has line outs and a small amplifier for the headphones, it cannot run speakers directly.
The sounds could be highly pitched after hooking up your Yamaha HS50M through M-Audio FasTrack Pro due to having a bad connection or lack of compatibility. You can troubleshoot this by checking the compatibility of the device and the connection made. Contact Customer Support for more help