In 1 Sam. 20:25, why does עַל-מוֹשָׁבוֹ appear to have two te'amim?

Question

I understand that there is a rule (with rare exceptions) that a single word cannot bear two Masoretic accents. However, I have not seen 1 Sam. 20:25 listed as one of the exceptions:

וַיֵּ֣שֶׁב הַ֠מֶּלֶךְ עַל־מ֨וֹשָׁב֜וֹ כְּפַ֣עַם ׀ בְּפַ֗עַם אֶל־מוֹשַׁב֙ הַקִּ֔יר וַיָּ֨קָם֙ יְה֣וֹנָתָ֔ן וַיֵּ֥שֶׁב אַבְנֵ֖ר מִצַּ֣ד שָׁא֑וּל וַיִּפָּקֵ֖ד מְק֥וֹם דָּוִֽד׃

And the king sat upon his seat, as at other times, even upon the seat by the wall; and Jonathan stood up, and Abner sat by Saul's side; but David's place was empty.

I have also read that azla "occasionally replaces metheg to mark secondary stress," but I am not confident that this can logically apply here (if so how?).

What I wasn't understanding was that, with the preposition joined by maqqef, the "secondary accent" syllable receiving the kadma is not "the first syllable of the word." For Wickes, p. 113, says, "Azla may take the place of light Metheg in the same word with Geresh (only of course not on the first letter)." If this is a valid rule, then the word moshav with the two accents would be illegal, but I suppose `al-moshav is another animal.

How common is the phenomenon exemplified by the accentuation of the word moshav here?

Answer 1

You seem to have mostly answered your question. For the purposes of cantillation, words that are connected with a maqaf are treated as one word.

Thus, על־מושבו (a) has a syllable (מו) that's appropriate for a light accent (געיה קלה), (b) which is not on the first syllable (because על is the first syllable), (c) the word is not preceded by a conjunctive accent. R. Breuer (in טעמי המקרא section ג.10-11) says that in this situation, the light accent becomes a kadma (or azla, if you will) only when not in the domain of a revia. Here, however, revia does follow, and R. Breuer lists this among several exceptions (along with Lev 14:51, Deut 25:19, and Sam 1:4:18). He suggests that perhaps the transformation still occurs when t'lisha g'dola precedes, even with a revia following. However, he lists another 14 exceptions to that suggestion, so at the end we're left with a general rule and some exceptions — whether your verse is an exception or not is up in the air.

Overall, using this site as a database (while imperfect, it's close enough for generalities): the Torah contains 37 occurrences of geresh and kadma on the same word, as compared to 1076 plain geresh and 509 gershayim; thus, about 2.3% of geresh/gershayim occurrences in the Torah have a kadma on the same word. You can check the other books yourself, but I imagine you'll find a similar spread.