Help with "sorting by composer"

Hello to all of you,

I'm writing this subject to get some help. I'm trying to sort my music by composers on iTunes 11. So, I write down the "Composer" like "Johann Sebastian Bach", and everything is fine on the composer view : I have "Johann Sebastian Bach" :

Then I'm going to the "Sort by composer" Field, and I write "Bach" for all the Johan Sebastian Bach Music. I'm closing iTunes and reopen it (or else, composer view is not refreshed - perhaps there is a trick to force refreshing ?) and TADAM, my Bach entry becomes two :

I've tried to change the view with Option+J, but nothing works, I've got two Johann Sebastian Bach, and two Bach/Busoni.

So I'm cleaning the "sort by composer" field, and the two Johan Sebastian Bach becomes one entry again.

It does the same with a lot of others composers. Don't know how to get the things right...

Could someone help me ?

Thanks in advance.