Being new to Apple and the iPhone, and, being unable to find any info on how the music was stored in the iPhone, I incorrectly assumed that it would be converted to one of the Apple m4a formats. Therefore, I created a special folder just for iPhone music, and used dB Poweramp to convert the relevant files to the Apple lossless format. (A playlist is not practical since the base files are stored on external drives that may not always be connected.) Once the music was on the phone, about 900 files, I realized that having ignored album art all these years was a mistake, and I had to correct a substantial number of files to keep the displays being "unknown album" and "unknown artist" with no album art. However, only a little of the album art was switched around initially.
Then I ran into the synchronization nightmares, starting when I tried to correct files a few at a time. I ended up manually deleting the files from the phone and from the library, re-adding them to the library, then synchronizing, to avoid iTunes and/or the iPhone "remembering" the previous information. Since the synchronization doesn't always do anything, I finally decided that it would be easier just to delete the entire library in iTunes, and re-add it.
That's convenient when the library consists only of that one folder: resynchronizing with the empty library, re-adding the folder to the library, then synchronizing again, works sometimes. Then, however, I ran into the problem that the music on the iPhone would not get deleted despite iTunes having warned me that it would; when it kept not working, I even started using two user accounts on my pc to synchronize, just to get the warning that the phone is synchronized with "another" library and all the music will be deleted (yes, yes, that's what I want: if only it would do it instead of just warning me about it.) (After running into many hours worth of these nightmares, no more will I threaten to get a Mac; the iPhone has given me a heads-up on what to expect.) (And, yes, I did try the fix of renaming the folder inside the Roaming folder and killing syncserver.exe in the task manager, which also works sometimes.) NONE of the fixes I have found are 100% effective. (I think I've tried everything, even unchecking sync "music" as well as syncing music. I do wonder--should I perhaps run iTunes "as administrator"? Here's a hint: when the music will not delete off the iPhone, I think that adding just one song to the library instead of deleting the entire thing makes it work. I did have some instances where there was music on the phone when iTunes insisted there was none. Those are nightmares worthy of Windows.)
The deal on my album art is that it IS what I want: it is all embedded by dB or by MP3Tag. I don't want Apple touching it. In some cases, I converted the music from analog and no album art is available on the internet, so I made do with scans, etc., but there is nothing for Apple to mess with. The album art issue became overwhelming when I realized that Apple was just as happy with mp3 files as with its own format, giving me more space for music, so I got rid of the m4a files and used mp3s. The album art got completely loony. I synchronized, rebooted, synchronized again, numerous times, rebooted the phone and the computer, used different user accounts, and, eventually, it would synchronize. I worked on all the id3 tags manually, and, without realizing what it was that finally did it, I had everything perfect.
The entire library of album art got probably 75% switched around AGAIN, after everything was perfect, and I realized that the problem was the id tag. I had fixed all the original files in my limited library "Music for iPhone," but not my entire non-iTunes library (>10,000 songs.) When I added just a few new songs to my special folder, it would not re-synchronize, forcing me to delete all/re-synchronize, resuting in the new library on the iPhone (not in iTunes) being completely messed up.
I then realized that those few new songs I had added had not been processed by MP3Tag. At this point, it helps to realize that Windows has a severe problem with album art also: Vista and Win7 both lose it sometimes unless you use MP3Tag to upgrade tag compatibility. For instance, the ID tag on "The Crystal Ship" by the Doors, as read by MP3Tag, is only ID3v1 as it comes out of the cd, but processing with MP3Tag adds ID3v2.3, which seems to make the difference. Processing all one's music files with MP3Tag seems to help with both Windows and Apple.
There is a potential complication: for the iPhone, I changed some of the id tags so that there would be fewer "album" listings. For my actual library, I add the disc number of multi-disc sets to the name of the album, but for the limited library of my iPhone, I have changed the titles so that all the songs from one box set have the same album name. I don't want to look at the album list and see the same box set showing as 6 different albums, even though they are different "volumes" or "discs." So I changed tracks with album titles "Complete Anthology, disc [whatever]" to just "Complete Anthology." I foresee a possible problem if the same album has different artwork on different files, but we will see. Another possible issue, which I could envision causing an problem, is that some files have multiple pieces of artwork. dB poweramp allows you to add multiple pieces of album art, such as a photo of the band and/or a photo of a flyer and/or the back album cover and/or any of a number of other things. We shall see.
