Hi all,
Thanks to everyone for your work here. I feel like a really, really dumb guy reading through all of these posts to make sense of how to do this. After a lot of reading I finally understand and I want to share a zip folder with everything collected here and a set of instructions. Hopefully this helps other people like me who are genuinely nowhere close to as smart as masagrator and Arpeggiate.
Google Drive Link to download .zip file
INSTRUCTIONS:
*addendum
* I didn't mention how to make Music.pck. It feels like so long ago that I did that, I forgot how, it's somewhere on page 1 of this thread
* Also open XBCX Music Tracks.csv to figure out the HEX of the song you want to replace.
1. Open "ConvertWAVtoWEMthenChangeExtensiontoWAV" folder
2. Install foobar2000-x64_v2.25.6.exe
3. Install foo_input_vgmstream.fb2k-component
4. Move Music.pck to the directory that has unpack_digits.bat in it.
5. Run unpack_digits.bat, rename the Music folder to "Music_digits".
6. Run unpack_hex.bat, don't rename the Music folder.
7. Open your desired audio track in foobar.
8. Right click the track, press "convert" > "..." > "Convert"
9. Give the converted wav file a name. The name will be the HEX of the song you're replacing.
10. Move the converted wav file to the folder: ConvertWavToRIFFOpus
11. Drag and drop the converted wav file on to DROP_here.cmd, leave the command window open.
12. Move the newly created wem file to "ChangeExtensions" folder.
13. Change the file extension of the .wem file to .wav (just hit rename and change ".wem" to ".wav", trust me, it works for this step!)
14. Move newly created .wav file into the "STREAMS" folder.
15. Navigate to "BANKS" folder, double click "extract.bat"
16. Navigate to "bgm" folder, open HIRC.json in Notepad++
17. Ctrl+F, find the HEX that matches the song you want to replace.
18. Right below the HEX you will see "SrcDuration" and "Duration" and "Position" that have the SAME VALUES, change these three SAME values into the milliseconds from the command window in step 11.
19. Save the HIRC file.
20. Navigate to "BANKS" folder, double click "pack.bat".
21. Navigate to "PACKED" folder, move the newly created bgm file into the "BANKS" folder.
22. Navigate back and double click Pack.bat, this will create a new Music.pck file in the "PACKED" folder.
23. Move Music.pck to Atmosphere/contents/0100453019AA8000/romfs/sound/Music.pck
24. Pat yourself on the back, you earned it.