blocking midi output of included files

[Federico Bruni]

I have several files who have the \midi block and I have included them 
in a new file - book.ly - (which, surprise surprise, I use to produce 
a book).

I need the midi block in each file, because they are still in progress 
and I have to check the music.
But I'd like to tell LilyPond to not produce new midi files when I 
compile book.ly

There's a way to do so?

Thanks for help!

Federico
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