Tremolo in MIDI

[Andrew Bernard]

I am new to MIDI output, so pardon me if a stupid question, but a
search of the user archives did not reveal anything.

According to the supported notation for MIDI in the NR, using \repeat
tremolo instead of :n works. Yet this MWE produces no tremolo in the
MIDI (as far as I can hear). What do I need to add to make it work? It
would be a pity if this can't be made to work because the very piece I
am setting is the usual New Complexity type of work for a woodwind
instrument and it just so happens that about 15% of the piece is
tremolo, so it would tedious to emulate tremolo by hand.

Andrew

%=====

\version "2.21.6"

music = {
 c''4 d''
 \repeat tremolo 4 c''16 c''4 |
 d'' \repeat tremolo 4 g'16
 c'2 |
}

\score {
  \new Staff { \music }
  \layout { }
  \midi { }
}