MSP stands for MUD Sound Protocol. If you wish to use sound (and your client supports it), type 'config MSP' within the mud to activate it. You can then use the 'msp' command to toggle the different sound categories on and off. Download and unzip the soundpack file into the MUSHclient\sound folder.
WAV soundpack (20.1 MB)
The previous MP3 soundpack is available on request, but (despite being smaller) has the major drawback that you can only play one sound at a time. Make sure you've set the 'msp' command to WAV format.