\version "2.22.2"

\new PianoStaff <<
  \new Staff = "up" {
    % enforce creation of all contexts at this point of time
    <>
    \change Staff = "down"
    c,4 d, e, f, | g, a, b, c | d e f g | a b c' d' |
    \change Staff = "up"
    e' f' g'  a' | b' c'' d'' e'' | f'' g'' a'' b'' | c'''1 |
  }
  \new Staff = "down" {
    \clef bass
    % keep staff alive
    \repeat unfold 8 s1 
  }
>>