Recently I faced this issue when I try to sync music from iTunes library to my iPhone 5s. In Apple support communities, a lot of users reported the same issue. They getting music sync issue with their devices like iPhone 6, iPhone 4, iPad 2 and iPod touch 5G.
Fix 1:- (Disable Find my iPhone)
Go to iPhone iCloud settings and disable “Find my iPhone”.
- First copy all your music to the following folder: “Music\iTunes\iTunes Media\Music”.
- Uncheck “Sync Music in iTunes” option. iTunes will ask you to delete all existing music on your device. Select OK and click Apply.
- Again check “Sync Music in iTunes” option and then click “Apply”.
If this method does not work turn off “Convert higher bitrate songs to 128kbps”.
Fix 3:- (Delete Music)
First turn off “Sync music”. Go to Usage -> Manage storage on the iOS device and delete music.
Fix 4:- (Delete Non-music files)
- First backup your device using iTunes or iCloud.
- Navigate to iTunes Music folder and delete all non-music files.
- Restore your iPhone from backup. Then re-add all music again.
- In iTunes uncheck “Sync Music” option.
- Navigate to General -> Usage -> Manage Storage. Delete all music. Now recheck “Sync Music” option again.
- Go to iTunes summary tab and select the following options:“Sync only checked songs and videos”, “Manually manage music and videos”.
- Try to Sync again.
- On your iPhone, iPad or iPod, reset network settings via Settings -> General -> Reset Network Settings.
- Choose “Trust this computer”.
- Go to iTunes summary tab and choose the box next to “manually manage music and videos.”
- Then try to sync.
- Drag and drop playlist on your iPad or iPhone.
- Connect your iOS device to the computer via USB cable. When Sync stuck with “Waiting for changes to be applied” message, unplug it and plug it again. The music sync will continue where it stopped.