BGMを切り替えてボリュームも設定できます。
設定を記憶します。

<script type="text/javascript"><!--
soundsrc=new Array("swonderful.mid","furudokei.mid","araitate2.mid"); //ファイル
soundtitle=new Array("ス・ワンダフル","おじいさんの古時計","恋心");   //タイトル
sv=7;                         //初期音量 0〜10
theDay=1;                     //記憶日数
sw=170;                       //スライドバーの幅
//-------------------------------------------
theName="bgm=";
document.write("<bgsound id='bgs'loop='infinite' src=''>");
document.write("<form name='form1'><select name='select1'>");
for(i in soundsrc)
  document.write("<option value='"+soundsrc[i]+"'>"+soundtitle[i]+"</option>");
document.write("</select><input type='button'value='選曲'");
document.write("onClick='document.all.bgs.src=this.form.select1.value;selectno=this.form.select1.selectedIndex'>");
document.write("</form>");
document.write("<table vspace=0 cellspacing=0 width="+sw+"><tr onmousedown='mc=0'style='cursor:hand'>");
for(i=0;i<=10;i++)
  document.write("<td id='v"+i+"'onmouseover='vol("+i+")'height=16></td>");
document.write("</tr></table>");
mc=0;sc=sv;
selectno=0;
function vol(sv){
  if(mc)return;
  sc=sv;
  s=(-(sv-10)*(sv-10)+100)*100-10000;
  document.all.bgs.volume=s;
for(i=0;i<=10;i++){
  if(i<=sv){document.all("v"+i).style.backgroundColor="#3399ff";}
  else {document.all("v"+i).style.backgroundColor="#cccccc";}
 (sv==i)?document.all("v"+i).title=sv:document.all("v"+i).title="";}
}

function bgm_set(){
 theCookie=document.cookie+";";
 start=theCookie.indexOf(theName);
if(start !=-1){
  end=theCookie.indexOf(";",start);
  theData=unescape(theCookie.substring(start+theName.length,end));
  setbgm=theData.match(/[^,]+/g);
  sv=setbgm[1];
  selectno=setbgm[0];
}
  document.all.bgs.src=document.form1.select1.options[selectno].value;
  document.form1.select1.selectedIndex=selectno;
vol(sv);
}

function cook_set(){
  setDay=new Date();
  myData=selectno+","+sc ;
  setDay.setTime(setDay.getTime()+(theDay*1000*60*60*24));
  document.cookie=theName+escape(myData)+";expires="+setDay.toGMTString();
}
window.onload = function(){bgm_set();mc=1;};
document.body.onmouseup = function(){mc=1;};
window.onunload = function(){cook_set();};
document.body.onselectstart = function(){return false;};
/* himajin.moo.jp */
// --></script>