function musicOff() {
document.midi.stop()
}
function musicOn() {
document.midi.play()
}
function changeButton() {
if (document.onoff.B1.value=='Turn music off') {
document.onoff.B1.value='Turn music on';
musicOff()
}
else {
document.onoff.B1.value='Turn music off';
musicOn()
  }
}