If did you want.........

 
<script language="javascript">
function doSearch() {

 //document.all.searchg.q.value = '"' + document.all.searchg.q_.value + '" ((intitle:index.of mp3) | ("index of" + "mp3") | ("index of" + inurl:mp3) | ("index of" + intitle:mp3)) -html -htm -php -asp -txt -pls';
 document.all.searchg.q.value = '"' + document.all.searchg.q_.value + '" intitle:index.of mp3 -html -htm -php -asp -txt -pls';
 return true;
}
</script>

<form onSubmit="return(doSearch());" name="searchg" method="get" action="http://www.google.com/search" target="_blank">
<input type="hidden" name="q" value="">
<input class="small_text" type="text" name="q_" size="42" maxlength="255" value="">
<input class="small_text"  type="submit" name="sa" value="Search">