What the Kitten Plays

Zez Confrey wrote "Kitten on the Keys" in 1921 after hearing his grandmother's cat walk across her piano. What does a walking cat actually play? Wikipedia's article on cats gives two facts about the walk. A cat paces: both legs on one side move together. And it registers directly: each hind paw comes down close to where the fore paw on that side has just been. Put those on a keyboard at true scale and every note gets played twice.

Red prints are the left paws, along the front edge of the keys, so they can only hit white keys. Blue prints are the right paws, further back where the black keys stand. Each step plays two notes: the fore paw lands on a new key, and the hind paw lands on the key that fore paw struck one step earlier on that side. Paler notes in the score are those echoes.

What follows from the scale

A modern octave spans 164–165 mm, so a white key is about 23.5 mm and a black key 13.7 mm. At the default stride of 14 cm, each step on one side moves about six white keys, a seventh. The two sides land half a stride apart, about three white keys, so the fore paws together climb the keyboard in fourths, and every one of those notes comes back a step later under a hind paw. The back paws hit a black key whenever a step happens to land on one.

What stands on what