Changing LilyPond instrument names midscore

Long and short instrument names change on the fly.

   \paper {
      ragged-right = ##t
      left-margin = 30
      indent = 0
   }

   \new Staff {
      \override Staff.TimeSignature #'stencil = ##f
      \override Score.BarNumber #'transparent = ##t
      \set Staff.instrumentName = \markup { \hcenter-in #14 "Flauto" }
      \set Staff.shortInstrumentName = \markup { \hcenter-in #14 "Fl." }
      c'1 \break
      c'1 \break
      \set Staff.instrumentName = \markup { \column {
         \hcenter-in #14 \line { "Flauto" }
         \hcenter-in #14 \line { "contralto" } } }
      \set Staff.shortInstrumentName = \markup { \column {
         \hcenter-in #14 \line { "Fl." }
         \hcenter-in #14 \line { "contr." } } }
      c'1 \break
      c'1 \break
   }