MIDI & repeats

[Benjamin Tordoff]

Hi all, I’m wondering if there’s a smart way to make the midi output for a 
particular part do the following two things (both common in Sousa marches):

1. Have a part play only on 2nd time through the repeat.
2. Have different dynamic for 1st and 2nd times through repeat.

A minimal example of how I would typically typeset this is below but produces 
midi output that plays all repeats with uniform volume. I've had a good hunt 
around the internet for examples of doing this but either I'm searching for the 
wrong things or this is a somewhat obscure request!

Thanks in advance.

Ben


\version "2.23.10"

notes = {
  \repeat volta 2 {
    <>^\markup{(2nd time only)}
    c''1 | c''1 |
  }
  \repeat volta 2 {
    <>_\markup {\dynamic "pp" "(2nd time " \dynamic "ff" ")"}
    d''1 | d''1 |
  }
}

\score { % PDF output
  << \new Staff \notes >>
  \layout {}
}

\score { % MIDI output
  \unfoldRepeats << \new Staff \notes >>
  \midi {}
}