Hi Pang,
This won't help for MIDI, as has been pointed out, but you did not specify that.
Here's my function for metronome marks, which allows you to use notes in them. I have a whole bunch of related functions, some with boxes, some with additional text parameters and so on. You can obviously put any number you like in here. [I have edited this a little, because I use custom had made fonts for notes and I just deleted all that for this example to help, so it may not be quite so beautiful as in my own context.]
I am pretty sure every man and his dog is going to criticise the idea of a metro mark of 72.5, as players, if this is for humans, can't attain that accuracy. No metronome I have, mechanical or digital, will let me set a fractional tempo. Just saying.
Andrew
%=====
metroMark =
#(define-event-function (duration arg y-offset)
(ly:duration? markup? (number? 0))
#{
^\markup
{
%\with-color #(x11-color 'grey50)
\raise #y-offset \concat {
{
\score {
\new Staff \with {
\remove "Staff_symbol_engraver"
\remove "Time_signature_engraver"
\remove "Clef_engraver"
}
{ \relative c'' { \stemUp \omit Accidental c$duration } }
\layout {
indent = 0
ragged-right = ##t
}
}
}
\sans \fontsize #-1 #arg
}
}
#})
%====