Helmholtz pitch notation

Helmholtz pitch notation is a system for naming musical notes of the Western chromatic scale. Developed by the German scientist Hermann von Helmholtz, it uses a combination of upper and lower case letters (A to G), and the sub- and super-prime symbols ( ͵  ′ ) to describe each individual note of the scale. It is one of two formal systems for naming notes in a particular octave, the other being scientific pitch notation.