Parshat Bamidbar: In the presence of Aaron their father - but who did what?

In parshat Bamidbar, we read {Bemidbar 3:4}:

ג אֵלֶּה, שְׁמוֹת בְּנֵי אַהֲרֹן, הַכֹּהֲנִים, הַמְּשֻׁחִים--אֲשֶׁר-מִלֵּא יָדָם, לְכַהֵן.	3 These are the names of the sons of Aaron, the priests that were anointed, whom he consecrated to minister in the priest's office.
ד וַיָּמָת נָדָב וַאֲבִיהוּא לִפְנֵי ה בְּהַקְרִבָם אֵשׁ זָרָה לִפְנֵי ה, בְּמִדְבַּר סִינַי, וּבָנִים, לֹא-הָיוּ לָהֶם; וַיְכַהֵן אֶלְעָזָר וְאִיתָמָר, עַל-פְּנֵי אַהֲרֹן אֲבִיהֶם. {פ	4 And Nadab and Abihu died before the LORD, when they offered strange fire before the LORD, in the wilderness of Sinai, and they had no children; and Eleazar and Ithamar ministered in the priest's office in the presence of Aaron their father. {P}

There is a dispute amongst parshanim as to the meaning of עַל-פְּנֵי אַהֲרֹן אֲבִיהֶם at the end of pasuk 4. Rashi explains it as rendered in the JPS translation above, that they, Eleazar and Itamar, ministered in their father's lifetime. This certainly seems like the most straightforward explanation, especially in light of the previous pasuk.

Ramban, however, points to a parallel in Divrei Hayamim I 24:2:

א וְלִבְנֵי אַהֲרֹן, מַחְלְקוֹתָם: בְּנֵי אַהֲרֹן--נָדָב וַאֲבִיהוּא, אֶלְעָזָר וְאִיתָמָר.	1 And the courses of the sons of Aaron were these. The sons of Aaron: Nadab and Abihu, Eleazar and Ithamar.
ב וַיָּמָת נָדָב וַאֲבִיהוּא לִפְנֵי אֲבִיהֶם, וּבָנִים לֹא-הָיוּ לָהֶם; וַיְכַהֲנוּ, אֶלְעָזָר וְאִיתָמָר.	2 But Nadab and Abihu died before their father, and had no children; therefore Eleazar and Ithamar executed the priest's office.
ג וַיֶּחָלְקֵם דָּוִיד--וְצָדוֹק מִן-בְּנֵי אֶלְעָזָר, וַאֲחִימֶלֶךְ מִן-בְּנֵי אִיתָמָר: לִפְקֻדָּתָם, בַּעֲבֹדָתָם.	3 And David with Zadok of the sons of Eleazar, and Ahimelech of the sons of Ithamar, divided them according to their ordering in their service.

Ramban matches עַל-פְּנֵי אַהֲרֹן אֲבִיהֶם in parshat Bamidbar to לִפְנֵי אֲבִיהֶם in Divrei Hayamim, and therefore interprets the pasuk in Bamidbar differently. It is rather Nadav and Avihu (rather than Elezear and Itamar) who died (rather than ministered) עַל-פְּנֵי אַהֲרֹן אֲבִיהֶם (and also, of course לִפְנֵי ה). Thus, it the phrase attaches to a place much earlier in the verse, and much higher in the syntactic tree.

The trup appears to agree with Rashi's reading, putting the etnachta on lahem, thus clearly having עַל־פְּנֵ֖י אַֽהֲרֹ֥ן אֲבִיהֶֽם as part of the second portion of the verse.

א וְאֵ֛לֶּה תּֽוֹלְדֹ֥ת אַֽהֲרֹ֖ן וּמֹשֶׁ֑ה בְּי֗וֹם דִּבֶּ֧ר יְהוָ֛ה אֶת־מֹשֶׁ֖ה בְּהַ֥ר סִינָֽי׃ ב וְאֵ֛לֶּה שְׁמ֥וֹת בְּֽנֵי־אַהֲרֹ֖ן הַבְּכֹ֣ר ׀ נָדָ֑ב וַֽאֲבִיה֕וּא אֶלְעָזָ֖ר וְאִֽיתָמָֽר׃ ג אֵ֗לֶּה שְׁמוֹת֙ בְּנֵ֣י אַֽהֲרֹ֔ן הַכֹּֽהֲנִ֖ים הַמְּשֻׁחִ֑ים אֲשֶׁר־מִלֵּ֥א יָדָ֖ם לְכַהֵֽן׃ ד וַיָּ֣מָת נָדָ֣ב וַֽאֲבִיה֣וּא לִפְנֵ֣י יְהוָ֡ה בְּֽהַקְרִבָם֩ אֵ֨שׁ זָרָ֜ה לִפְנֵ֤י יְהוָה֙ בְּמִדְבַּ֣ר סִינַ֔י וּבָנִ֖ים לֹֽא־הָי֣וּ לָהֶ֑ם וַיְכַהֵ֤ן אֶלְעָזָר֙ וְאִ֣יתָמָ֔ר עַל־פְּנֵ֖י אַֽהֲרֹ֥ן אֲבִיהֶֽם׃ {פ

Shadal points this out, stating:

על פני אהרון אביהם : לדעת רמב"ן חוזר למעלה, וימת נדב ואביהוא על פני אהרן אביהם, וכן הוא בד"ה א' כ"ד ב ', והאתנח ראוי תחת ואיתמר (נתה"ש

Thus, Shadal appears to agree with Ramban's reading, but points out that the etnachta should go under the word veItamar.

As it currently stands:


Click on the image to see the trup tree. If we move the etnachta to Itamar, the first division moves to that point, and we can say (for instance) that עַל-פְּנֵי אַהֲרֹן אֲבִיהֶם modifies the entire first portion of the verse, where the main topic is Nadav and Avihu's death, with Eleazar and Itamar as an aside.

Shadal feels free to do this because he holds that the particular trup as we have it is post-Talmudic. What would Ramban say, though?

I would note the gemara in Chagiga 6b, where there is a machloket about the meaning of a specific pasuk in terms of which karbanot were brought, with the nafka mina being what trup there is (at least as Rashi explains it):

אל בעי רב חסדא האי קרא היכי כתיב (שמות כד) וישלח את נערי בני ישראל ויעלו עולות כבשים ויזבחו זבחים שלמים לה' פרים או דלמא אידי ואידי פרים הוו למאי נפקא מינה מר זוטרא אמר לפיסוק טעמים

Perhaps if this is really so we should move the position of etnachta when laining this Shabbos, and recalculate all the rest of the trup to match.

Perhaps one can point out the Wickes has the primary dichotomy as a logical one and all subsequent (minor) dichotomies as syntactic, and the present position of the etnachta is the one that divides the pasuk most into two discrete logical topics, even though it strands the last phrase in a syntactically invalid or awkward position.