bach wrote his book, the "essay on the true art of playing keyboard instruments" in 1755 while in berlin. this book is important for two reasons. it was the first book to teach players to use their thumbs, which is now standard practice. secondly it was the first to talk about emotion as being an important part of a performer's skills; as important as technical ability. it is still in use today as the reference book on how to correctly play the ornamentation and how to improvise in the late baroque style. bach wrote his autobiography in 1773. this shows that where his father was mainly influenced by religion, bach was influenced by ideas from art and philosophy. he had a collection of 400 paintings of people whose ideas and works he admired.