MC uses tags to show you your media files. Tags are stored in the files and MC imports them into its own database. These tags can be different from the physical folders and filenames on your disk.
I'm going to asume the Mac version is the same as Windows version in this respect but a small warning, I've not used the Mac version so some things might work differently from what I'm suggesting here.
If you're certain all your Beatles songs are perfectly organised on disk (ie, /Your Music Folder/The Beatles/Albums/01 - Tracks.mp3)
Try the following:
Navigate to Audio/Files
Select the path for The Beatles
Select All tracks from an album that is incorrectly displayed in MC's Artist or Album View
Right Click the Files/Tracks
Choose Library Tools
Choose Fill Properties from Filename
In the dialog box that pops up you can use templates to correct the artist, album and track names with the file and foldernames on disk.
For instance, if you've organised your files as follows: /The Beatles/Albums/01 - Tracks.mp3
you can use the following template to correct the values in MC:
Directories: [Artist]/[Album]
Filename: [Track #] - [Name]
If your files contain a . instead of a - to separate the track # from the name, simply adjust it in the filename field.
I suggest you try it out on a single album first and remember the undo function. If you mess up, simply press CTRL-Z or choose from the menu Edit/Undo.
You can also do the reverse. If your tags are good and MC shows everything perfectly, you can rename your files/folders to reflect MC's views. The feature works the same as above.