C is the tallest stack (blame the Cure primarily), followed very closely by B (Beatles and Blur and Bowie...), then S and then P and then M, less closely. There's nothing under Q (I must need a best of Queen) or Z. The X pile is actually not too shabby, though, thanks to XTC, X-Files soundtracks, and all those homemade compilations that my friends labeled "Xmas mix [fill in year]".
dirae and all_timeqb may be amused to know that when my son picked up the Judybats album "Down in the Shacks Where the Satellite Dishes Grow," he said in delight, "There's a dog in a backhoe!" I pointed out that it was actually a pickup truck, but yes, true about the dog.