function to replace notes by rests

[Marc Hohl]

Hi list,

I have a melody with some spoken passages, written like this:

c4 d e f \xNotes { b b b b } f e d c

Now I need a midi file that contains the "normal" notes only:

c4 d e f r r r r f e d c

As the file is a bit lengthy, I think of a way to just redefine
\xNotes to change every note to its corresponding rest, instead of 
rewriting the whole file (or using sed or any other external script).

Has anyone a scheme routine at hand that does exactly this job?

I remember vaguely that there has been something like this on the 
archives, but I did not find it again ...

TIA,

Marc