Could it be that this represents a system for generating music?

[Maruyama Toru]

There is a real theory and practice of grafting plants, ie creating "new" plants from the stems of one and the roots of another, etc... But this practice started in the 17th century.

This plant is not a real one; rather, it serves as a model for something else. After all, grafting would never be performed using an attachment like this. It is a symbol—a model—of something else entirely.