when encoding librettos from the 18th century based on several sources
we had to learn that it is impossible to use <app> combined with (or
embracing) structural elements such as <p>, <lg> and <l>.
Even though it is possible to use <app from "X" to "Y"> and to put the
<app>-element in the "restriction-free"-room following such structural
units it would often be much more easier and quicker to use a form as
the following one (please excuse, I miss the original example at the
moment and give a purely constructed one which is not ideal in any case
but should only show the unit which we wanted a mark "in one go"!):
<speaker>Somebody in despair</speaker>
<l>O look my problem here</l>
<l>Is not the empty beer!</>
<l>Instead I did not know</l>
<l>how to keep the effort low.</l>
<p>I don't dare to sing this silly refrain which is only
an illustration of tiny problems!</p>
What was the reason to forbid such structural embracing with an app-element?
If somebody is willing to give us a short hint why we sit on the wire
(as we say in German) in this case, we should be very gratful!
Thanks in advance,