I invite you to step outside the box of music notation to learn a way of understanding keyboard harmony that reveals underlying simplicity. I call it the PKH view after the first letters of the words of the main title of the document available from this website that describes it: Picturing Keyboard Harmony.
Keyboard harmony is much simpler than music notation makes it appear. The most complex looking harmony in conventional terms tends to be simpler on the keyboard than nominally simple key-signature harmony. Because music notation makes harmony appear complex, the conventional way of learning keyboard harmony is closely intertwined with developing keyboard expertise. Some substantial fraction of the ten-thousand or so hours required to become an expert pianist must be invested to come to an understanding of how sophisticated harmony plays out on the keyboard.
Not everyone who approaches the piano aspires to be an expert pianist and no one is expert to begin with. The PKH view separates understanding keyboard harmony from the development of keyboard expertise. The starting point is the observation that piano keys going up by octaves play pitches that double every octave, making them harmonically equivalent. This means that only twelve harmonically independent piano keys exist and only twelve symbols are needed to describe them. Developing this observation leads to a tonic-centered, key-signature-independent view of keyboard harmony that is simple and leaves nothing out. The notation that expresses this view evokes simple mental pictures of both the keyboard patterns of harmonic progressions and their harmonic meaning.
I am R.J.A. Buhr (the R stands for Raymond but I am usually called Ray or RJ), a retired (2000) Canadian Professor of Computer System Engineering now living in San Francisco.
I starting studying the piano in 1995 as an adult beginner with the intent of learning some of my favorite harmonically sophisticated pieces. These pieces are not technically difficult in a showers-of-notes sense, only harmonically sophisticated -- complex looking chromatic chord progressions, often difficult key signatures. My intent was to have fun, not to become an expert pianist. I wanted to bypass scales, exercises and harmonically unsophisticated beginner pieces to go directly to the real thing. I figured I knew enough about music from a lifetime of listening to it (and some experience playing trumpet as a youth), to figure out how harmony worked by playing it.
As piano lessons proceeded I became intrigued by the conceptual gap between the simple keyboard patterns I was being taught to voice sophisticated chord progressions and the inability of standard music notation to describe them directly in a simple way. I thought that if things are simple on the keyboard, there must be a way of capturing the simplicity in a notation. Trying to find such a notation became a substantial retirement hobby. I was confident in this endeavor because my academic specialty was developing notations for understanding and designing complex software systems -- notations that found their way into software designs worldwide -- and I thought that surely harmony could be no more complex. The successful result is described in the document Picturing Keyboard Harmony that is available from this website.