It's most likely the scipt you're using has a start up song (On Start) when mIRC initiates. As soon as mIRC loads up type whilst the song is playing:

//if ($insong.fname) echo -a $nopath($v1)

That'd return the filename you're playing.

If it doesn't return the actual artist/title of the track type something like this:

if ($insong.fname) echo -a $sound($v1).artist - $sound($v1).title

-Andy