The Pendulograph is a book written by John Andrew in 1881. The book is a series of bi-pendulum writings that explore the twenty ratios of the musical system, or sound seen in the silence. The book delves into the science behind sound and music, exploring the relationship between different ratios and the resulting musical notes. The author uses the pendulum as a metaphor for the oscillation of sound waves, and the book is filled with diagrams and illustrations...