One of the main goals of this class is to allow you to start improvising in a polyphonic (i.e., non-amateurish) way.
In each of our brains is a repository of musical ideas that we draw on when we improvise. Once something gets in that repository, it will be permanently available to you as an idea to use during your improvisations. Unfortunately, for most people, it is hard to start getting music in their repository!
Just playing music from score usually doesn’t get the music in your repository. I know lots of pianists who have played Beethoven’s “Für Elise” but very few of them can improvise in that style.
Using your inner ear in an active way while playing is the secret to getting music into your repository. Here are some ways to do that:
Improvisation. When you improvise something, even something very basic, it gets saved in the repository. This is the reason most music students can improvise on “I-IV-V-I”, since they’ve played around with it on the keyboard in their theory classes.
Playing by ear. Learning a piece from a recording rather than score is how jazz musicians have always learned to improvise. It works for classical musicians as well.
Transposition. When transposing, you see one thing but play another. It forces you to use your inner ear at the expense of your eyes. It is the tried-and-true way to learn how to improvise.
Knowledge. A deep understanding of the grammar and vocabulary of harmony gets the music into your repository. No musician can truly improvise without some sort of understanding of how the chords work together. There are lots of ways to analyze, but you have to find an analysis style that you personally understand.
Sightreading. For some people, sightreading uses their inner ear (there are also people who can do it without using their inner ear), and after sightreading a lot of Mozart sonatas, they can improvise a decent facsimile.
Of all of these, transposition is the most straight-forward, the quickest, and the simplest. So, we try to transpose everything we can in this class, in order to get as much music as possible into our repository.