How to write a sharp (#) or hash-tag in Lilypond markup

Question

I want to write a Cis (C-sharp) with markup{}.

I am aware that there is a difference between the usual hashtag sign # (used in commenting code or on twitter) and the muscial sharp sign ♯.

With the original sharp sign this code works well.

markup{C♯}

But I found out that it does not work with a hashtag even if it is escaped

markup{C#}
markup{C\#}

So why is that and how could this be solved without the original sharp sign?

Answer 1

Try:
\markup{C\sharp}

You might also like to make the symbol smaller and raise it up with \super, and and you'll probably want to concatenate the letter and symbol together with \concat; something like:

\markup{\concat{C\super\sharp}}

Answer 2

It is unclear to me what you want. You write

I am aware that there is a difference between the usual hashtag sign # (used in commenting code or on twitter) and the muscial sharp sign ♯.

And you state

With the original sharp sign this code works well. \markup{C♯}

Yet you appear to desire getting a hashtag sign instead of an accidental in a musical context. That makes little enough sense. Of course, LilyPond uses the hashtag sign for something different (introducing Scheme), and "it does not work with a hashtag even if it is escaped" is nonsensical in a language that does not use backslashes to escape special characters (other than in very specific in-string contexts).

It appears that you want \markup "C#" or in most contexts the simpler "C#" though it is unclear why.