Why idevicebackup2 do not backup music?

[Hiepars]

No description provided.

[nikias]

That's not how it works. The device controls the backup, so Apple decides what is part of the backup and what is not.

[Hiepars]

can you send my question to Apple?

[mexmer]

you music is backed up either on apple servers (in case you purchased it from store), or in your computer (if you uploaded it trough itunes). that's why apple deciced to not make second backup, same is true for videos in itunes application