Towards better Davening and Torah Learning
Let's start with the word that brought about the reader comments. First word in the 3-pasuk portion about the first Shabbat of Creation, which we say in the Amida of Leil Shabbat, repeat it right after the Amida, and say it as the first part of Friday night Kiddush.
vai-chu-LU, accent on the last syllable, but that isn't our focus at this moment. The second letter of the word is a YUD. It has a SH'VA under it. The SH'VA is NACH. There- fore, the YUD with its SH'VA close off the first syllable of the word, VA and YUD /SH'VA make VAI.
The YUD does not sound like a Y beginning the second syllable. Not Y'CHU - the YUD belongs to the first syllable.
On the one hand, this works well for the VAV/PATACH, since the PATACH is a short vowel and a letter with a short vowel does not usually stand alone as an "open syllable". It is usually closed off by another letter with a SH'VA NACH.
The problem is the CHAF after the YUD. By the rules of DAGESH KAL, there should be one in the CHAF, since it follows a SH'VA NACH. VAI-KU-LU. But we don't say that.
Had there been a DAGESH CHAZAK in the YUD, it would have done double duty, closing off the first syllable and beginning the second syllable. Then the CHAF would not even think of getting a DAGESH. But the YUD does not have a DAGESH in it.
Nonetheless, the rule seems to be that the SH'VA is NACH, the YUD/SH'VA closes the first syllable, and the following letter does not have a DAGESH.
Apparently, this bothered some DIKDUK people in the past sufficiently that they created a new type of SH'VA, in addition to the NA and the NACH. They called it a SH'VA M'RACHEIF, a floating SH'VA.
Having a third type of SH'VA resolved the problem of the missing DAGESH from the CHAF of VAI-CHU-LU. The only problem is that there are only two types of SH'VAs.
Here's a word from NITZAVIM with the same situation. 29:18 - BIL-VA-VO. The word for his heart, L'VAVO, has a SH'VA NA under the LAMED, which precludes a DAGESH KAL in the VET that follows it. With the BET prefix making the word BIL-VAVO, in his heart, the SH'VA changes to a NACH, and it becomes part of the first syllable of the word BIL. The BET/CHIRIK is not strong enough to let the LAMED stay with the rest of the word it is part of. That's one of the unusual features of this kind of SH'VA and it is what creates resistance to pronouncing these kind of words correctly.
29:28 - Here's another one. BANEINU, our children. L'VANEINU, to our children. The LAMED/SH'VA NA prefixed to the word causes the the DAGESH to drop from the BET. Not L'BANEINU, but L'VANEINU. So far, so good. Next comes the conjunctive VAV. The VAV/SH'VA (NA) it would have been becomes an U (SHURUK), because you cannot have two consecutive SH'VAs at the beginning of a word. And unlike a regular SHURUK that vowels another letter, which would produce a strong syllable by itself, this SHURUK is weak and takes the LAMED to its syllable, changes the SH'VA from NA to NACH and becomes UL. It might seem that the DAGESH should go back into the VET, following a SH'VA NACH as it does, but the DAGESH remains absent. UL-VA- NEI-NU. Not U-L'VA-NEI-NU.