[Mesorah] mees Hashem hay(')sa zos

[Michael Hamm]

The ArtScroll sidur has a sh'va na under the yod of "hay'sa" in
halel's "mees Hashem hay'sa zos", and I'm wondering why.  The general
rule, as far as I know, is that a stressed syllable (not with a meseg
but with the trop proper) does not make the sh'va after it na.  So
there are a few possibilities I can see:

1.  The general rule as far as I know is wrong.  There is no such rule.

2.  ArtScroll is wrong to make it na.

3.  I looked at the beginning of the Malbim Nach's copy of T'hilim
(not the new Malbim Nach but the older one, some thirty years old) and
it has there what it claims is a quote from R'VH about the trop on
T'hilim.  It says there that a mer'cha is sometimes used in place of a
meseg, and the following makaf dropped.  If that's the case, and if
hay(')sa has a mer'cha (as it does in the Malbim nach but not in the
Artscroll one-volume tanach, which has a shofar holech (munach) under
it), then maybe, just maybe, the use of a mer'cha where a meseg
"should be", for whatever reason it was substituted, did not change
the fact that the sh'va is na.

If anyone has any insight into this, I'd much appreciate hearing.

Gut voch,

Michael Hamm
Postdoctoral Research Scholar
Department of Psychiatry
Washington University in St. Louis
St. Louis, Mo. 63110
msh210 at gmail.com