music = {
  \key c \major a'4 g' f' e'
  \key ges \major ees' g' aes' ces''16  bes' beses' aes'
}

manual_transpose = {
  \key ees \major c''4 bes' aes' g'
  \key a \major fis' ais' b' d''16  cis'' c'' b'
}

\markup {  \line { Original, untransposed: } }
\music


\markup {  \line { Auto-transposed - 'c ees': } }
\transpose c ees \music


\markup {  \line { Manual key signature transpose (need to do this enharmonic translation automatically): } }

\manual_transpose