Passing music objects into scheme functions

[Charles Winston]

Hi developers,

I’m working on chord semantics and creating a new way to input chord name 
exceptions. I want the chord exceptions to be an alist whose keys are the 
chord's semantics list and values are the exception markups. I wrote a function 
that takes an event chord and a markup as parameters and returns an alist pair 
with the correct key and value. I’m trying to test my function, and I have this:

chordVar = \chordmode { c1:m7 }

markupVar = \markup { “min7” }

#(chordmode-to-exceptions chordVar markupVar)


On the last line I get the following error:

Wrong type argument in position 1 (expecting Prob): ()


When i do #(display chordVar) and #(display markupVar) their structures print 
what I expect. Could someone help me understand why this error could be 
happening?

Thanks,
Charles