Itunes shows songs on iphone, but music app does not

The problem here turned out to be a corrupted Itunes database. Because all my music is properly organized, it was fairly easy to create a new Itunes database. After that, the sync worked properly, and I got all my music onto the Iphone. I got suspicious when I discovered that half of my playlists were empty. So I went ahead and created a new database and then added the files in my top-level folder (all my music). I was able to recreate my playlists from the XML file using some software I had obtained earlier.

OK, I restored my Iphone. I initially looked at some songs/albums I knew were missing and they are still missing. I then used the "Iphone Storage" technique to delete the music and tried the sync again. No luck. I have 8500 songs in my Itunes library. However, when the sync is running, the number at the top is not even half of that number. It's like "n of 3750" even though Itunes says the correct number before I click on "SYNC". There's a bug someplace, or there is an artificial limit that I'm hitting. My Iphone has plenty of free storage. Is there a limit someplace is settings that I don't know about? BTW, this has worked before, but I could not tell you when it stopped working.