Fix subscripts in the Calc manual

* doc/misc/calc.texi (Musical Notes): Use @sub instead of TeX-only
'_' notation.  For the details, see the discussion in
https://lists.gnu.org/archive/html/emacs-devel/2023-06/msg00096.html.

diff --git a/doc/misc/calc.texi b/doc/misc/calc.texi
index 3ba1a9d4d150cfa1438a45cd2a1bbc48ac340b32..db6cad3450ce4a12b3a2af3fd18bd6676d78653f 100644 (file)
--- a/doc/misc/calc.texi
+++ b/doc/misc/calc.texi
@@ -28470,13 +28470,13 @@ B and
 @c flat and @expr{B}.
 the octave numbered 0 was chosen to correspond to the lowest
 audible frequency.  Using this system, middle C (about 261.625 Hz)
-corresponds to the note @expr{C} in octave 4 and is denoted
-@expr{C_4}.  Any frequency can be described by giving a note plus an
+corresponds to the note @slanted{C} in octave 4 and is denoted
+@slanted{C@sub{4}}.  Any frequency can be described by giving a note plus an
 offset in cents (where a cent is a ratio of frequencies so that a
 semitone consists of 100 cents).
 
 The midi note number system assigns numbers to notes so that
-@expr{C_(-1)} corresponds to the midi note number 0 and @expr{G_9}
+@slanted{C@sub{-1}} corresponds to the midi note number 0 and @slanted{G@sub{9}}
 corresponds to the midi note number 127.   A midi controller can have
 up to 128 keys and each midi note number from  0 to 127 corresponds to
 a possible key.