Amplitude (2003) has one extra song that was only released as a separate demo disk bundled in P.O.D.'s Album 'Payable on Death'.
This repo contains files that I used and modified to re-add the exclusive song into the main game.
For the .str files I used mfaudio to create them
They are Uncompressed PCM with 48000 hz frequency and 200 interleave
If you want to build your own disc you need Onyx Command Line to compile the configs to the format amp uses and arkhelper which is included in Mackiloha to extract and create .arks that amp also uses.
You are also going to need a copy of Amplitude (2003) and the Amplitude P.O.D demo.