You need to open inc/design.inc.php in your favorite text editor. Search for getSiteStat and scroll down till you see:

'pmu' => array('capt'=>_t("_Music"), 'query'=>"SELECT COUNT(`ID`) FROM `RayMusicFiles` WHERE `Approved`='true'",'link'=>'browseMusic.php','adm_query'=> "",'adm_link'=>""),

and just put // in front of that line. Save and you're done.