Problem with Lilypond functions

[jim.showalter]

I have searched the archives and cannot find why the following is happening.
They are contrived to demonstrate a larger problem.

This one works as expected

majorKey = #(define-music-function (parser location note ) (ly:music?)
#{
     a $note g
#})

{
  \majorKey g
}



But what I really want to do is something like this.

majorKey = #(define-music-function (parser location note ) (ly:music?)
#{
     \key $note \major
#})

{
  \majorKey g
}

I get an error message about that it is expecting  "\default or
NOTENAME_PITCH"  I get a similar error for
transpose.  Is there another variable type (other than ly:music) that should
be used?  Can anyone explain this behavior?

Thanks,
Jim