The E Major Prelude by Bach
This one has 4 sharps in the key signature. I can already hear the groans from some of my students. Its hard enough to play Bach all by itself, and then you have to remember the D# also. Life is not fair. However, there is a positive. There always is. This piece is so wonderful and lovely. After all the hard work of putting it together, we get a really nice piece of music to enjoy. Its also a great workout for our hands. Lots of good technique here.
Lets take a moment to examine the structure of the piece. How it starts, where it goes, and how it ends. It starts in E Major. True to prelude style it keeps to a pattern, the best way to describe it is back and forth rotating sixteenths with a repeating finger. (There probably is a better way to describe this prelude but I gave it my best shot from the top of my head). Anyway, this pattern continues through the whole piece. That's why we call it a prelude. It starts in E Major, like I said earlier, and then it moves to the dominant. It moves to B Major. The transition happens with the use of an A# note. With lots of A#'s we eventually are convinced that B Major is the new key. On the second half of the prelude we go into a few quick key changes. A Major, C# Minor, before we start making our way back to E Major again. Measure 17 we have a D natural, which keeps us away from E Major, but measures 18 and 19 gives us D# with a good cadence and we are back home. Started in E Major, and ended in E Major. Enjoy!