How to define a macro that expands to a percussion "pitch"?

[Darren Ng]

[subject] How to define a macro that expands to a percussion "pitch"?

input is

    m = hh
    \drummode { \m 8 \m  r4 \m  }

expected output should be equivalent to

    \drummode { hh8  hh8 r4 hh4 }

actual output (console)

    percussion.ly:*:*: warning: Ignoring non-music expression

        \m 8 \m r4 \m
    percussion.ly:*:*: warning: Ignoring non-music expression
        \m 8
             \m r4 \m
    percussion.ly:*:*: warning: Ignoring non-music expression
        \m 8 \m r4
                   \m

actual output (midi)

    (I hear no percussion at all)