+Accidentals (including naturals) may be used for modifying scale steps.
+These are entered by appending @code{+} (for sharps), @code{-} (for flats)
+or @code{!} (for naturals) after the number. For double accidentals the
+modifier is applied twice. For the modification of the third step the
+number is often omitted, which can be achieved by using @code{_} instead
+of a number.