Midi-channels in Frescobaldi (Newbie)

[Ben Engbers]

Hi,

I am working on Linux/Fedora with Frescobaldi 3.3.0
I have installed fluidsynth and Qsynth and Rosegarden as midi-editors(?) 
and now in Frescobaldi I can play the score I am editing. The sound that 
is produced by the laptop is quite acceptable.

This is part of my score:
MelodiePart = \new Staff \with {
  midiInstrument = "french horn"
} { \clef "treble_8" \Melodie }
leadSheetPart = <<
  \new ChordNames \chordNames  \new FretBoards \chordNames
  \new ChoirStaff <<
    \new Staff {
      \set Staff.midiInstrument = #"electric guitar (jazz)"
      \set Staff.midiMaximumVolume = #0.7
      \new Voice { \voiceOne \ChordLine }
      }
    \new Staff \with {
    midiInstrument = "acoustic guitar (nylon)"
  } { \clef "treble_8" \BaseLine } >>
>>

\score {
  <<
    \MelodiePart    \leadSheetPart  >>
  \layout { }
  \midi {    \tempo 4=160  }
}

As you can see I have 3 different instruments. Both in Qsynth and 
Rosegarden, these channels are shown.
My question is how (if possible) the characteristics (room, damp, width, 
level etc) can be adjusted. Is it only possible to change the 
characterics for all channels combined or is it also possible to adjust 
the channels separately? Should this be done in Frescobaldi/lilypond 
before creating the midi-file or is this something that is done in a 
midi-editor such as Rosegarden?

Ben