Trying to write a scheme function

[dfro]

Hello everyone,
I would like to create a function that transforms one note to another 
using scheme's cond procedure. This is what I have working so far using 
an arg of type number?:

%start code
\version "2.22.2"

tNote =
#(define-scheme-function
  (note)
  (number?)
  (_i "Transform one note to another using cond")
  (cond ((= note 1) #{ { c } #})
        ((= note 2) #{ { c' } #})
        ((= note 3) #{ { c''2 } #})
        (else #{ s #})
        )
  )


{ \tNote 1 \tNote 5 \tNote 2 \tNote 3 }
%end code

_________

I want the type to be ly:music? and the cond procedure to evaluate a 
note rather than a number. The following code does not work (I get an 
'Unbound variable" error), but I think it shows what I am trying to do:

%start code
\version "2.22.2"

tNote =
#(define-scheme-function
  (note)
  (ly:music?)
  (_i "Transform one note to another using cond")
  (cond ((= note c,) #{ { c } #})
        ((= note d,) #{ { c' } #})
        ((= note e,2) #{ { c''2 } #})
        (else #{ s #})
        )
  )


{ \tNote c, \tNote f \tNote d, \tNote e,2 }
%end code

_________

Should I be creating a music function rather than a scheme function?

Any thoughts on how to get this working and why it works? Thanks for any 
help and for the mailing list.

Peace,
David