This is a little off topic from your original question (and sorry if I'm posting in the wrong place - I usually don't engage on forums or social media in general, so way out of the loop on etiquette). However, I'm delving for the first time into the same kind of modifications you are talking about (adjusting incorrect notes, improving fretting for personal preference). Would love some advice on how to make this work.
I got as far as importing a song through DLC Builder, and converting the audio file so that I could open the XML in EOF. From there, I was able to tweak the notes for more accuracy and save a new XML, but haven't been able to import that back into a .PSARC that Rocksmith will recognize. I swapped the new XML for the old, clicked "Build Release" in DLC Builder to create a new file (with some errors that I ignored, thinking they may have been remnants from the original file, maybe not though?), but the song won't come up in my list in the game. I could add another few pages with my questions and all the things I likely did wrong, but don't want to overburden you here if this isn't the right place. But in general looking for the right forum to get some specific advice without spending hours sorting through search results that don't quite answer my questions (3-4 hours in and nothing to show for it so far, lol).
Any input would be appreciated. Thanks.