itunes on a PC Windows 11 Pro latest update, iPhone 15 Pro running Ios 17.3
SOLVED (at least for me with a library of almost 4000 tracks in it)
Having just experienced a similar problem. My itunes music library is stored locally on my PC and I had just added a new track to my itunes library, went to sync my phone with the PC itunes and it was really slow and appeared to hang on stage 3 of 5 - 'preparing to sync'. After leaving this for about 30 mins it was clear that something was not right. So stopped the sync. Looking at the iphone media under the iphone tab in the side menu in itunes almost all of the existing music would not play and were greyed out with a dotted ring alongside each track.
After inspecting the Windows system process logs a lot of trial and error trying to identify the source ofthe problem I came down to the conclusion that for whatever reason the sync process had got corrupted and this had resulted in the itunes internal data being corrupted and was now blocking any subsequent attemp to sync from that point on. All my music was in my itunes 'home' library and would play perfectly, but the iphone library tab obviously had a problem.
My solution....which works perfectly if your home library is on your PC and is complete and okay - check the number of tracks it displays and compare it to your phones music count in settings/general/about. If they are as expected then proceed. Mine was 3927 on the PC and 3926 on the iphone, the missing track was the new one I had just added to my itunes library.
1: If you have an iwatch - turn it off completely, only turn it back on after the complete process is done..
2: Put your iphone in aeroplane mode
3: Reboot your phone.
4: On the PC, do a full reboot and do not load anything.
5: Connect your phone to your PC with your data cable, and wait for Windows to "ping" which says it has seen the iphone is connected vis a usb port.
6: Start itunes
7: Click the iphone icon in itunes and look at the summary page
8: Make sure for now that you have the local source selected for the backup and not the cloud - again for now.
9: Click the music tab immediately under the summary tab in the vertical menu on the left.
10: Unclick the Sync box outside the details box and accept the warning that this will clear all your music from the iphone - again you should only do this if your library is local to the PC and complete and woking.
11: your ihpne should now have been cleared of all tracks and references to it, and more importantly the itunes database of the iphone library will also have been reset.
12: Close itunes and reboot both your PC and iphone.
13: Reconnect your iphone to your PC after it has booted up and wait for the connection "ping" on the PC.
14: Open itunes on the PC, wait for the iphone icon to appear and click it.
15: Click the music option under the "summary" tab and re-enable the Sync tab on that page, and make sure you have the complete liabrary option selected in the info box.
16: Return to the summary page ensure you are still set to local storage for the backup, then click the Sync button 17: Now just wait, the backup should proceed and run fairly quickly, then the syncing of the tracks should run very quickly - m,y 4000 tracks took approx 3 mins to complete. Close itunes.
18: Check your iphone music app to see that the tracks are there and play correctly,
19: Disable aeroplane mode on your iphone, and reboot both the ipone and PC.
20: Restart your iwatch, and give it a few minutes to reconnect to your phone.
All the restarts are essential to ensure that the drivers and system service processes in memory that handle the communicatrions between the devices are cleanly loaded each time.
Good luck, this worked for me and I apologise if my instructions aren't phased exactly as per the various screens but I just typed this from memory!