calculation of the total duration of a score

[Marc Hohl]

Hi list,

I have a couple of songs in my latest theatre project. It would be nice
to have something like "duration: 3'22''" at the end of each song.

Doing this by hand is straightforward:I generate a midi file that sounds
accurate and let it play by timidity – but IMHO it would be less tedious
and less error-prone if lilypond were capable of doing these
calculations itself.

Tempo indications and meter changes have to be taken into account, so
this is probably doable with a special engraver only IIUC.

Has someone else already done something like this? I have no experience
in writing scheme engravers, so any hint would be highly appreciated.

Thanks in advance,

Marc