Then when I bought a new Mac, I transferred the music from my phone to the Mac.
That's not how it was intended to be done.
iTunes: How to move [or copy] your music [library] to a new computer [or another drive] - http://support.apple.com/kb/HT4527
Quick answer if you use iTunes' default preferences settings: Copy the entire iTunes folder (and in doing so all its subfolders and files) intact to the other drive. Open iTunes and immediately hold down the Option (alt) key (shift on Windows), then guide it to the new location of the library.
Windows users see tip at: https://discussions.apple.com/message/18879381
You can add files to iTunes by dragging them to the "Automatically Add to iTunes" folder.
iTunes 9: Understanding the "Automatically Add to iTunes" folder. - http://support.apple.com/kb/HT3832 - Files put into this folder are actually moved from this folder onto the correct location in the iTunes Media folder.
It may be the volume got adjusted in the files. In iTunes get information on those two files and check under options.
Thanks for getting me started, Limnos. I wonder why I thought the beauty and simplicity of the system was that whenever you connected an iPhone to iTunes on a computer, the oldest music would be updated automatically?
I decided to use the home share version of transferring, and now that I have the share open on my home computer, I find that there are only those two songs on my Mac that are already on my Windows computer listed under shared/music. All the music that I have is listed under library/music. So how do I move that music file from library down to my shared music?
I can't remember the exact sequence of events here but this is what happened:
I turned on sharing on both computers so I guess they were connected to each other. Then I went to Finder and dragged the first 5 albums available into the "Automatically Add to iTunes" folder. And for some reason I looked at iTunes and my entire library was now already there. In spite of that, I dragged the rest of them into the folder anyway.
So they're now on the Mac under shared/my music, with them arranged alphabetically by artist. If I go one level below that, so it's under shared/music, I think all the music is still there, but I can't figure out how they are arranged. It certainly isn't alphabetical, but at least all the albums are still in one piece.
Here's what I don't like: as soon as I turn off the Windows computer, the share button on my Mac iTunes disappears, so all of the music disappears with it and it's only to be found on the Finder again. Is there a way to move it into iTunes permanently, so I don't need Windows turned on?