This video shows Stephen Malinowski playing the first movement of Beethovens Moonlight Sonata. The sheet music scrolls by at the bottom, and a bar graph scrolls across the top.
The colors indicate the «pitch class» of the notes; that is, every C# is a certain color (blue), every E is a certain color (olive green), etc. The piece is in the key of C# minor, so there’s lots of blue and green, especially at the beginning and end. What data is this bar graph reflecting? Can you think of a different way to represent this data?