What's a moment?

[Peter Chubb]

Hi,
        Reading the scheme code and the documentation, I'm struggling
with the concept of a moment in Lilypond.  The documentation says it's
a rational number that represents a moment in musical time.
Therefore there should be a way to add a duration to a moment to get
another moment.  But there doesn't seem to be.  Likewise, there *are*
functions for adding, subtracting, multiplying and dividing moments.
Which makes no sense if a moment is a point in time.

So what *is* a moment?  What do the numerator and denominator
represent?  Beats?  Bar numbers?  Milliseconds from the start of the
piece?  Inquiring minds want to know.


--
Dr Peter Chubb  http://www.gelato.unsw.edu.au  peterc AT gelato.unsw.edu.au
http://www.ertos.nicta.com.au           ERTOS within National ICT Australia
A university is a non-profit organisation only in the sense that it
spends everything it gets  ... Luca Turin.