LilyPond is a software to produce musical engravings (notations) using modern musical symbols. It works with text input. It is more akin to programming than using graphics. As a result the musician doesn’t have to bother with the details of the layout. The changelog page has some good examples of how LilyPond takes input to generate the correct symbols. A set of quality manuals from the author gets anyone who studies music start digitizing their musical notes quickly.
LilyPond is free and open source. It supports Linux, Windows and Mac.