Music folder on PC Missing Some Of The Artists Names In File

For example the song Drive My Car by The Beatles. In iTunes under the song summary, it shows it is located in:

C:\username\Itunes Music\music\_ _\Rubber Soul\Drive My Car.mp3

It is missing The Beatles name as the artist. I have included them as the artist, and it works for most songs, but not all. Can't seem to see the difference in the ones that work and the ones that don't. Any ideas how to correct?