It was very interesting to read a book by one of the masters, one specifically meant for instruction. As a professional musician myself, I found that most of the concepts he introduced were familiar to me, but the terms and notation he used differ from ours. Due to the evolution of musical styles since this book was written, his advice (while interesting and correct) is not always practical for the modern musician delving into genres outside of classical. I found this book most interesting as an insight into how Music Theory used to be taught. It also includes many exercises for practice. I would not recommend using this book to actually learn music theory. Enjoy it as a word from Tchaikovsky, but seek out a theory class for legitimate training.