\[
semitone = 12 \times log_2 \frac{freq}{440} + 69
\]
\bibitem{Jang_start}Jang, Jyh-Shing Roger \& Gao, Ming-Yang. (2000). \emph{A Query-by-Singing System based on Dynamic Programming}.
the International Workshop on Intelligent Systems Resolutions (the 8th Bellman Continuum), PP. 85-89, Hsinchu, Taiwan, Dec 2000.
