Is there a way to set the midiInstrument for ChordNames with FretBoards?

[Kevin Cole]

Hi,

I have a score with an outline shown below. I managed to get the vocal
part doing "choir aahs", and the piano defaults to a piano instrument,
but is there a way to have ChordNames / FretBoards do anything with
"acoustic guitar (nylon)"?  Even if the playback isn't super accurate
in terms of duration, it seems like, with the fretboards, it would be
able to have a half-educated notion of which notes to sound.)

(And, is there a better way to set the "choir aahs" -- without
changing the whole thing around too much? It somehow feels redundant
to add "\new Staff" around the "\new Voice" since the staff was
already showing without it, but I couldn't get the MIDI to sound
without adding the "\new Staff".)

Thanks.

%%%%%%%%
\version "2.22.1"
\language "english"

global = {
  \time 2/4
  \key c \major
  \tempo 4 = 80
}

chordNames = \chordmode   { ... }
melody     = \relative c' { ... }
words      = \lyricmode   { ... }
upper      = \relative c' { ... }
lower      = \relative c  { ... }

\score {
  <<
    \new ChordNames \chordNames
    \new FretBoards \chordNames
    \new Staff \with { midiInstrument = #"choir aahs" }
    <<
      \new Voice = "mel" { \melody }
    >>
    \new Lyrics \lyricsto mel \words
    \new PianoStaff
    <<
      \new Staff = "upper" \upper
      \new Staff = "lower" \lower
    >>
  >>
  \layout { }
  \midi   { }
}
%%%%%%%%