[Tex/LaTex] Writing musical pitches

Question

Is there a package or macro that allows me to easily typeset musical pitches, like the following:

? Indeed I would like to have subscripts for the octaves. Let's say

$\mathrm{E}\flat_3$

How would I write a macro producing this output, when the invocation is

\note{Eb3}

Like:

\newcommand{\note}[1]{???}

I would have to take the string apart, the first char goes into \mathrm, then there is an optional second char # or b, followed by a digit.

Answer 1

The only quirk is that you have to use brackets [] rather than braces {} to enclose the argument.

\documentclass{article}
\def\note[#1#2#3]{#1\if b#2$\flat_#3$\else\if#2##$\sharp_#3$\else$_#2$\fi\fi}
\begin{document}
\note[Eb3]
\note[A2]
\note[F#4]
\end{document}

If you would prefer the use of braces to brackets, then the following modification would do. It renames the \note from the above code as \xnote and creates a newcommand \note to do the argument translation.

\documentclass{article}
\newcommand\note[1]{\xnote[#1]}
\def\xnote[#1#2#3]{#1\if b#2$\flat_#3$\else\if#2##$\sharp_#3$\else$_#2$\fi\fi}
\begin{document}
\note{Eb3}
\note{A2}
\note{F#4}
\end{document}

---

Since egreg's answer seems to go beyond what the OP asked, providing reasonable behavior when either argument 2, argument 3, or arguments 2 and 3 are missing, I felt it incumbent to do the same (EDITED using Qrrbrrbr...brbrbrl's suggestion to enclose subscript definitions in braces, which will facilitate two-digit octave numbers, shown in last line of output):

\documentclass{article}
\newcommand\note[1]{\xnote#1\relax\relax\relax}
\def\xnote#1#2#3\relax{#1\if#2\relax\else\if b#2$\flat\if#3\relax%
  \else_{#3}\fi$\else\if###2$\sharp\if#3\relax\else_{#3}\fi$\else$_{#2}$\fi\fi\fi}
\begin{document}
\note{Eb3}
\note{A2}
\note{C#}
\note{A}
\note{Eb}
\note{F#4}

\note{F{14}}
\note{F#{14}}
\end{document}