Can only see music purchased from iTune Store - where are my other albums?

Had to reinstall Mac OS-X High Sierra. On opening iTunes for the first time I was compelled to login to the iTunes Store. Since then I can only see the Music albums etc I purchased through the store. All the other music I had in my library (imported from CDs etc) has disappeared.

Even when I double click on the old iTunes library on a removable HD that I connected I get the same albums so it's not to do with the .itl file.

What's going on, anyone know?