Are you saying that as you download the song you want to adjust it's volume/mix?

What the ???

If you use XMMS or WinAmp (and possibly other proper mp3 players, as opposed to one built in as a second thought to a peer-to-peer filesharing program) you will be able to set the volume/mix and save an auto-load-default, (but save the auto-loadd-default probably only once the song is fully downloaded).

Is that what you were talking about?