I already have it implemented in my first game in Batari Basic "Invasion".
I'm not a musician at all but I have a friend who composes in chiptune for my mobile and C64 games, I'll see if passing him the explanation of how TIA works with volume, waveform and frequency he can compose something for the intro screen.
Could I ask you a favor, could you pass me the code of the sample tune that you have here in the post, so I study it with him and it's more representative than one of the 15 FXs.
Thanks in advance!😁👾🕹️