\change Voice

[Dan Eble]

Would it be hard to make \change Voice work as below without relying on the 
extra “X” context?
— 
Dan

\version "2.19.17"

\layout {
  \context {
    \name "X"
    \type "Engraver_group"
  }
  \context {
    \Voice
    \accepts "X"
    \defaultchild "X"
  }
}

\new Staff <<
  \context Voice = "one" \with { \voiceOneStyle } {
    f'2 \change Voice = "two" f'2
  }
  \context Voice = "two" \with { \voiceTwoStyle } {
    s1
  }
>>