Sorry, I had an important exam and then I forgot. I found the source in a backup. I can compile it with Delphi 6 Professional (@hikaru: also in a virtual machine
It requires two 3rd party units: Trayicon.pas and AMixer.pas (I modified the second one a bit so that it's not a VCL component anymore). They're both freeware:Trayicon.pas on koders.comAMixer.pas: TAudioMixer
I'd put my own code under GPL, but I doubt that's possible, because I use these two units...
So, for now, it's just freeware with source provided - please mention me in the copyright remarks of derived works.