{alias itunes {

The extra bracket can and will gum up the entire works.

That's not to mention the outrageous case of brackets you got going.

alias itunes {
  if ($1 == open) {
    .comopen itunes itunes.application
    .echo -a $comerr
  }
}
if ($1 == play) { 
  .set %play $com(itunes,PlayPause,3)
  /track
  if (!%play) {
    .echo -a iTunes may not be open.
  }
}
if ($1 == Next) {
  .set %next $com(itunes,NextTrack,3)
  /track
  if (!%next) {  
    .echo -a iTunes may not be open.
  }
}

Closes the alias leaving a bunch of floating if errors waiting to happen.

Which begs the question: How is this "improved?" Also whom did you steal this off of because it is blatantly clear that you did not 1.) Proofread 2.) Make it yourself, because if you did such clerical errors would be non-existent ESPECIALLY on a snippet that requires indefinite more precision than the average text event.

This is actualy one of my best scripts yet.. Not saying much at this point. :/