Cause #1 - The songs are not listed to have the same album artist or are not listed as a compilation in iTunes.Should your music player just put all songs with the same album name together? Probably not. Do you own a greatest hits album? What if you own "Greatest Hits" by Michael Jackson and "Greatest Hits" by Pink Floyd? Would you be happy if they were combined together in your music player? Maybe! But, maybe not. The point here is that having the same album name is not always enough information to clump the two albums together. Enter "Album Artist" and "Compilation" in iTunes.
Let's take a look at the album "I Love The 70's" in iTunes
As we can see, the artist is not the same for every song. But it is the same album. Unfortunately, your music player may not see it this way...
Now right-click and select "Get Info"
You'll need to confirm that you realize that these changes will affect all of the files selected.
Now we can do one of two things. You can set the "Album Artist" or...
You can set that these songs are part of a compilation. Now let's re-run iSyncr and see what we get.
Wait! It still looks bad! What happened!! Well, iSyncr doesn't remove songs unless you ask it to. In this case, I forgot to check "Remove Music Not In These Playlists" in the USB app, or select "Remove Abandoned" in the WiFi app. So we are looking at the old songs and the new songs.
After telling iSyncr to remove the old versions of the songs, I now have what I expected all along. One album. Woot!