MIDI commands are not emitted in repetitions

[Bruno]

Hi all,

I have been working on chord charts which I wanted to use as the input for
my arranger to generate MIDI backing files, I wanted to use Program Change
messages to switch the sections of the auto-accompaniment. While trying to
achieve that I found the following bug:

% somewhere in the included file:
pc_fillB =  \set Staff.midiInstrument = #"pad 1 (new age)"

% in the file itself:
intro = \chordmode {
    \repeat percent 2 { c1 a:m f \pc_fillB g }
}

In the resulting MIDI file the Program Change message is sent only once, at
the beginning of the 4th bar. All the 8 bars of notes are generated
properly. Yes, I understand that Lilypond is *not* a MIDI sequencer :-)

Thanks in advance for the time of everyone who cares to look into it.

Bruno