Imagine you have a toy box full of different toys, and you want to play with them all at the same time. That's kind of like what a Petrushka chord is!
A Petrushka chord is a special type of chord that is made up of multiple notes played at the same time. It's named after a Russian fairy tale character named Petrushka who was half-puppet and half-human.
To create a Petrushka chord, you take three specific notes and play them together on a piano or other instrument. The three notes are usually the root note (the note that the chord is based on), the note that is four scale degrees higher than the root note, and the note that is seven scale degrees higher than the root note.
So for example, if the root note of your chord is C, the other two notes you would add would be F (since it's four scale degrees higher than C) and G (since it's seven scale degrees higher than C). When you play all three notes at once, you create a Petrushka chord.
Petrushka chords are often used in music to create a feeling of tension or unease. They don't always sound very "pretty" on their own, but they can add a lot of interest and depth to a piece of music when used in the right way.