Re: [frogs] Da Capos, Codas and Segnos

[David Kastrup]

Marc Hohl <address@hidden> writes:

> I have also thought about implementing this properly.
>
> I  had the idea to extend the \repeat syntax:
>
> \repeat segno {.A.}
> \alternative {{ .B. }{ .C.}}

That appears quite preferable to me.  One problem I see is that there
sometimes is a number of repeat structures.  And sometimes a number of
ways to keep them unnested.

I have here a piece.  This has more or less the following parts:
[unlabeled], 2, 3, Coda.  Those parts are more or less formatted as
separate movements (possibly with vertical space above them, all
starting on a system of their own) but have to be played continuously.

Each of the parts (except the Coda) has its own repeat structure.  And
pretty much each of them are not anticipated in Lilypond.

Ok, here to the parts.

Part1:

Here we start at the beginning and go through once into the first
alternative labelled "Folge" and jump over the second alternative
labelled "Fine" into the repeat volta.  We do the first alternative
"1.", repeat the repeat volta and go into the second alternative "2.".
Then we jump back to the segno at "Valse 1", now using the "Fine"
alternative.

The advantage over a D.S. al Coda is that it is nuisance to have to
visually jump over a long part just for a single chord Coda.

Note that "Fine" has just two beats and anticipates a key change to B
flat major.

Ok, now part 2 is a bit too subtle for my taste.

We start with the missing upbeat from part 1's "Fine" in B major.  There
is a repeat volta which is not uncommon.  At the end of the second
repeat alternative, we have "D.S. al ||".  It turns out that "||" is not
a double bar, but rather the caesura/breathmark before the repeat volta.
There is no other caesura, and part 3 begins with a 2/4 upbeat
complementing the bar before the caesura.

Now we might be of the opinion that this score has provided us with
enough crazy tasks for typesetting (the anticipated key change at the
end of something formatted as a movement is rather tricky, I guess) and
for \unfoldRepeats, but no such luck.

Here is part 3:

Now part 3 is unique in that it has an optional repetition.  I can't
actually reliably guess the meaning.

The first alternative is labelled "(ad lib)" and has a parenthesized
segno and key change.  If you take the ad lib, execution is back to
parenthesized segno and then into second repeat alternative.

What happens if you don't take the ad lib repetition?  In that case,
three interpretations:

Play alternatives 1&2
Play just alternative 1
Play just alternative 2

It makes most sense musically to skip the first repeat alternative
completely (1&2 is conceivable, but changes the character of the
ending).  Which makes it somewhat nonsensical to have everything inside
of that alternative parenthesized, since once you decide you take the
first alternative, the material inside is not optional.

The last part, "Coda", obviously, starts in F major.  It has no repeats
and is off-topic.

-- 
David Kastrup