Usage of the Sch'wa nekuda

Question

I noticed there are many questions on Mi Yodeya to clarify the pronunciation of the Sch'wa na vs. Sch'wa nach, both having the same nekuda אְ, with elaborate rules distinguishing the two. It seems this controversy could have been completely avoided if the Sch'wa nach would not be marked at all, i.e. א. I assume the masoretes invented this nekuda at the same time as the other vowel signs. What was the reason to use the Sch'wa nekuda in both cases as opposed to only the case of Sch'wa na, which somewhat resembles the vowel?

Answer 1

Geoffrey Khan has the following proposal (Vowel Length and Syllable Structure in the Tiberian Tradition of Biblical Hebrew, p. 57), which requires some understanding of the Tiberian reading tradition to appreciate.

In the Tiberian reading tradition, long vowels appeared in more closed syllables than in modern reading traditions, and was in fact the general rule. There is evidence (some presented in the above article) that in such syllables, an epenthetic vowel would be added before the closing consonant. For example, שָׁמְרוּ would be pronounced /šɔ̄-ɔm-rū/, where the super-long syllable /šɔ̄m/ would be opened up by an epenthetic /ɔ/ (the sound of kamatz). Elsewhere (here, p. 289), Khan writes that the "furtive pataḥ" (the /a/ in רוּחַ /rū-aḥ/) is this same epenthetic vowel, just with a different vowel quality due to the following gutteral.

Now we can understand when Khan writes (emphasis mine):

In the early masoretic and grammatical sources there are allusions to the fact that the šəwa was sometimes mobile. In fact there may have been a degree of variation among individual readers as to whether a šəwa in a given word was made mobile or quiescent. The alternation between mobile or quiescent šəwa did not change the word form in any significant way. In each case the preceding vowel was long and was appropriate for secondary stress: שָׁמְרוּ = šɔ̄-mə-rū ~ šɔ̄-ɔm-rū. ru. It may be said that in these structures there existed a non-distinctive phonotactic variation: consonant + epenthetic ~ epenthetic + consonant. It was doubtless on account of this non-distinctive alternation that both quiescent and mobile šəwa were represented by the same sign.