Hi I'm new to the whole Rock Band 3 Custom scene, so I tried to upgrading a song (adding some missing notes, forcing some strums for rhythm and upgrading it to Pro guitar and bass) with Editor On Fire (EoF)
For a start I extracted the .con file and JUST touched the .mid updating the guitar and bass charts, then using CON Tools I cleaned the MiDi with MIDI Cleaner and created the .con with CON Creator, I was able to load the whole thing into RB3 but when I play the song (select and instrument and difficulty) the song starts and the band is warming up then the guitar/bass icon appears and the band does the finishing animation and it takes me to the score screen with, of course 0 score 0 stars. I edited another chart and when the song is loading, the game freezes leading me to reset the Xbox.
After that I go to the pratice menu and THEN I could play the song that didn't freeze the console normally with the changes I made but while practicing.
Remember I'm new to this and couldn't find much info on how to edit customs for RB3 let alone make them (wich I would enjoy to make)