I got this same error trying to sync from my Macbook Pro (OSX Yosemite, 10.10.5) to my iPhone SE. Oddly, the problem didn't occur with my previous iPhone 5s. The solution was simple - it was a permissions problem like JennyMGA26 said. On the Mac, here are the steps I took to fix:
* Note the song that fails, on my case it was a Zeppelin song.
* Using the terminal, cd to the directory containing the song
* Run `ls -la` and note the owner of the file that fails, in my case it was an alternate username I was using at one point, let's say that username is paulhewson
* Run `sudo find . -user paulhewson` from the top level music directory (~/Music), this shows all the music that is owned by this alternate user
* This command will change the owner to your normal username, in this case my real username is hewson: `sudo find . -user paulhewson -exec chown hewson {} +`
I suspect this error could result from any sort of permission problem, in some cases maybe read-only or locked files, in which case you'd want to chmod or unlock the files. If there are multiple types of permission problems, you may need to repeat this process a few times. Might be easier to chmod/chown everything in music, but I tried to avoid that so I didn't cause other issues.