I've been having a problem with syncing music to iPod gen4 and and iPod gen3 for some time now. There are similar issues reported in a variety of questions on this forum: after syncing, apparently successfully via iTunes, you disconnect the iPod and the iPod appears to have no music on it. However, I have not been able to find any that present to me a working solution, nor have a found a discussions which shares particular details of the situation that I am experiencing.
After a "no music on iPod after sync" experience, the iPod will no longer function properly after this, and you have to put it into disk mode in order to connect to the computer and "do a restore." The first time this happened, I didn't know about restoring, and actually discarded the iPod (a gen 3) and replaced it with my first gen 4. Now I have an additional gen 4 (my 2nd), plus I also purchased a used gen 3 to replace the one I threw away. Each of these three devices has experienced the problem, and I can get the device functioning again after restore. All the devices seem to be in good working shape and serve me fine; I do not believe that any of them has a hardware problem such as failing hard drive etc.
The problem of "no music on iPod after sync" can be created in a repeatable fashion by choosing the appropriate set of playlists to sync. I visited an Apple Store genius bar twice now to discuss the issue, and the conclusion was that there possibly was a "corrupt file" that was causing the problem. However, I can also reliably sync the music by splitting it into smaller pieces. For example, suppose I have a group of 20 playlist folders, and I choose to sync the first 10. This can be done without problem. If I then choose to sync the last 10 but without the first 10, this also can be done without problem. However, if I sync all 20 together, then I get the "no music" screen on the iPod after the sync. So I can load and play all the music files involved with my problem. What seems to be associated with the occurrence of a "no music" event is the volume of songs that I sync.
I am working with a large number of audio files organized into a large number of playlists arranged in a somewhat large number of playlist folders, some nested inside others. I suspect that a cause of the problem may be the large number of files and/or playlists and/or folders.
For instance, in my latest experience, I worked with a collection of files that I have sitting all together in one playlist folder, that itself sits inside a higher level playlist folder.. In this collection there are 4358 "songs" (the audio files aren't actually music) occupying 1.68 GB of memory. So I have one playlist folder (level 1, let's say) that contains within it a playlist (sub)folder (level 2) that has within it 36 playlist folders (level 3), each with a set of playlists inside that together account for all 4358 songs, without any repetitions of the songs between playlists. Some of the playlist folders contain as many as 206 playlists. The playlists vary in the number of songs they contain; I think there are some with just one or two, and I now there are some with at least 32 songs.
Anyway, with the above described collection, I can sync the first half of the set of level 3 playlist folders without problem. I can sync the second half of the level 3 playlist folders without problem. But if I sync all together, I have problems.
Any ideas as to what's going on here?