You could technically use TWTM language books and bend it to CM simply by cutting out a lot of the memorization and redundant repeating of rules. However, I found that it actually creates more work for the mom to do it that way. The difference between TWTM and CM is just a huge difference in how children learn, not necessarily what they learn. So you can use a classical style curriculum and simply make it gentle. And that doesn't mean lighter, just the approach to learning is easier. We started out classical and switched because my children do not respond to the classical approach very well. The article linked above is a good one, and there are several articles comparing the two with a slant to CM style. About the only books from a classical education we have held onto are SOTW and the IEW or Writing with ease books. For language, math, and science, we use a CM approach. Hope that helps.