When (in seconds) does each page begin?

[Matt Wallis]

I would like to obtain timing information to tell me at how many seconds 
into the score each page begins. I have had a go at this, and failed. So 
I'm now looking for answers to two questions:

1. How to obtain this output from lilypond (e.g. a file listing the 
number of seconds into the score at which each page begins.), and

2. Why does my attempt (see below) not work? I'm new to this type of 
deeper digging into lilypond, and I hope to learn from my mistakes.



What have I tried so far?

I guessed that the page-break-event might occur at the times of interest 
to me.

Looking at 
http://lilypond.org/doc/v2.19/Documentation/notation/saving-music-events-to-a-file, 
I modified event-listener.ly in an attempt to catch the 
page-break-event, like so:

----
% New function to handle the event:

#(define (format-page engraver event)
   (print-line engraver
               "page"))

% add a listener for the event:
#(define event-listener-engraver
  (make-engraver
    (listeners
     (page-break-event . format-page)
     (tempo-change-event . format-tempo)
     (rest-event . format-rest)
etc ...

----
This didn't produce the output I was looking for (no 'page' in the 
generated .notes files)

So I wondered (just guessing) if I needed to change the context to which 
event-listener-engraver was being added, do I changed that as follows:

----
\layout {
  \context {
    %\Voice     %% try a broader context :Score:
    \Score
    \consists #event-listener-engraver
  }
}
----

No joy.

My final hack was to add handling for the line-break-event and 
page-turn-event. Again no joy.

I am out of my depth. Have I perhaps just exposed the fact that I don't 
properly understand the interplay between events, contexts and 
engravers? Is there some difference between the page-break-event and the 
the events that are properly handled by event-listener.ly ?

Matt