Well, I now include an image; I usually write a "long underscore" when
there
is something that lasts in a next syllable; like in the example, "Sa --
cra
-- men __ tum" (here you can see what i mean in "men __ tum", or "to
__que"). I do not give trace about the syllable to be sung after "cer --
nu
-- i". The "i"
<http://lilypond.1069038.n5.nabble.com/file/n166284/Appunto_Tantum_ergo.jpg>
must be sung for the other three notes; is there a "rule" that says what
should be done? I hope to have expressed myself in a comprehensible way.
Thanks.