Lilypond
The LaTeX of music notation. It is a formatting language for music notation that has to be compiled into various output formats. The input file is a plain-text file making it very good with version control systems.
Notes, chords, and scales
<<lilypond-paper>>
{ c d e f g a b c' }
\relative d' { c d e f g a b c' }
<<lilypond-paper>>
\chordmode { c1 d e f g a b c' }
Paper configuration
\paper {
indent=10\mm
oddFooterMarkup=##f
}