Well using AS3 to read the ID3 Tags is probably not the way to go. You can of course use PHP, C#, Python or any other language to read the ID3 tags out of an MP3.
For instance you can have a PHP Script "id3Reader.php?file=mymp3.php" and will return an XML containing all the ID3 info, then you can parse that in AS3 which is rather quick. I recommend using caching in the PHP part or probably having a data store like mysql so you don t have to be reading the id3 tag over an over. Although PHP is a rotten language it does its job and for this kind of task it does it well.
Reading ID3 with PHP
http://php.net/manual/en/ref.id3.php