Well, you see I said before in my 10th song "Multiversal" that I no longer use Rolling Tones to make musics. I've just discovered that when the tmx file (Song extension for the app) is too big, it get corrupted.
I found a way to avoid that : Making song in multiples parts!
And thanks to that technique, I can then assemble them with Audacity and making extras things like tempo changes, scale changes etc rather than only one possibility in one song.
I can't wait to make my next song with that breand new technique! XD