As evident from a Sefer Torah, the Song of the Sea has structure unlike the rest of the text of the Torah. Such use of structure is an interesting way of adding to the meaning of the Torah without violating Deut. 4:2 (below), with הַדָּבָר taken to signify that no word may be added or subtracted. Use of structured text does neither.
(ב) לֹ֣א תֹסִ֗פוּ עַל־הַדָּבָר֙ אֲשֶׁ֤ר אָנֹכִי֙ מְצַוֶּ֣ה אֶתְכֶ֔ם וְלֹ֥א תִגְרְע֖וּ מִמֶּ֑נּוּ לִשְׁמֹ֗ר אֶת־מִצְוֺת֙ יקוק אֱלֹֽקֵיכֶ֔ם אֲשֶׁ֥ר אָנֹכִ֖י מְצַוֶּ֥ה אֶתְכֶֽם׃
(2) You shall not add anything to what I command you or take anything away from it, but keep the commandments of your God יקוק that I enjoin upon you.
As many have commented, the structure of the Song of the Sea is likened to a brick wall.
אָ֣ז יָשִֽׁיר מֹשֶׁה֩ וּבְנֵ֨י יִשְׂרָאֵ֜ל אֶת הַשִּׁירָ֤ה הַזֹּאת֙ לַֽיקוק וַיֹּאמְר֖וּ
לֵאמֹ֑ר אָשִׁ֤ירָה לַֽיקוק כִּֽי גָאֹ֣ה גָּאָ֔ה ס֥וּס
וְרֹכְב֖וֹ רָמָ֥ה בַיָּֽם׃ עׇזִּ֤י וְזִמְרָת֙ יָ֔-הּ וַֽיְהִי לִ֖י
לִֽישׁוּעָ֑ה זֶ֤ה אֵ-לִי֙ וְאַנְוֵ֔הוּ אֱלֹקֵ֥י
אָבִ֖י וַאֲרֹמְמֶֽנְהוּ׃ יקוק אִ֣ישׁ מִלְחָמָ֑ה יקוק
שְׁמֽוֹ׃ מַרְכְּבֹ֥ת פַּרְעֹ֛ה וְחֵיל֖וֹ יָרָ֣ה בַיָּ֑ם וּמִבְחַ֥ר
שָֽׁלִשָׁ֖יו טֻבְּע֥וּ בְיַם סֽוּף׃ תְּהֹמֹ֖ת יְכַסְיֻ֑מוּ יָרְד֥וּ בִמְצוֹלֹ֖ת כְּמוֹ
אָֽבֶן׃ יְמִֽינְךָ֣ יקוק נֶאְדָּרִ֖י בַּכֹּ֑חַ יְמִֽינְךָ֥
יקוק תִּרְעַ֥ץ אוֹיֵֽב׃ וּבְרֹ֥ב גְּאוֹנְךָ֖ תַּהֲרֹ֣ס
קָמֶ֑יךָ תְּשַׁלַּח֙ חֲרֹ֣נְךָ֔ יֹאכְלֵ֖מוֹ כַּקַּֽשׁ׃ וּבְר֤וּחַ
אַפֶּ֙יךָ֙ נֶ֣עֶרְמוּ מַ֔יִם נִצְּב֥וּ כְמוֹ נֵ֖ד
נֹזְלִ֑ים קָֽפְא֥וּ תְהֹמֹ֖ת בְּלֶב יָֽם׃ אָמַ֥ר
אוֹיֵ֛ב אֶרְדֹּ֥ף אַשִּׂ֖יג אֲחַלֵּ֣ק שָׁלָ֑ל תִּמְלָאֵ֣מוֹ
נַפְשִׁ֔י אָרִ֣יק חַרְבִּ֔י תּוֹרִישֵׁ֖מוֹ יָדִֽי׃ נָשַׁ֥פְתָּ
בְרוּחֲךָ֖ כִּסָּ֣מוֹ יָ֑ם צָֽלְלוּ֙ כַּֽעוֹפֶ֔רֶת בְּמַ֖יִם
אַדִּירִֽים׃ מִֽי כָמֹ֤כָה בָּֽאֵלִם֙ יקוק מִ֥י
כָּמֹ֖כָה נֶאְדָּ֣ר בַּקֹּ֑דֶשׁ נוֹרָ֥א תְהִלֹּ֖ת עֹ֥שֵׂה
פֶֽלֶא׃ נָטִ֙יתָ֙ יְמִ֣ינְךָ֔ תִּבְלָעֵ֖מוֹ אָֽרֶץ׃ נָחִ֥יתָ
בְחַסְדְּךָ֖ עַם ז֣וּ גָּאָ֑לְתָּ נֵהַ֥לְתָּ בְעׇזְּךָ֖ אֶל נְוֵ֥ה
קׇדְשֶֽׁךָ׃ שָֽׁמְע֥וּ עַמִּ֖ים יִרְגָּז֑וּן חִ֣יל
אָחַ֔ז יֹשְׁבֵ֖י פְּלָֽשֶׁת׃ אָ֤ז נִבְהֲלוּ֙ אַלּוּפֵ֣י
אֱד֔וֹם אֵילֵ֣י מוֹאָ֔ב יֹֽאחֲזֵ֖מוֹ רָ֑עַ נָמֹ֕גוּ
כֹּ֖ל יֹשְׁבֵ֥י כְנָֽעַן׃ תִּפֹּ֨ל עֲלֵיהֶ֤ם אֵימָ֙תָה֙
וָפַ֔חַד בִּגְדֹ֥ל זְרוֹעֲךָ֖ יִדְּמ֣וּ כָּאָ֑בֶן עַד
יַעֲבֹ֤ר עַמְּךָ֙ יקוק עַֽד יַעֲבֹ֖ר עַם ז֥וּ
קָנִֽיתָ׃ תְּבִאֵ֗מוֹ וְתִטָּעֵ֙מוֹ֙ בְּהַ֣ר נַחֲלָֽתְךָ֔ מָכ֧וֹן
לְשִׁבְתְּךָ֛ פָּעַ֖לְתָּ יקוק מִקְּדָ֕שׁ אדושם כּוֹנְנ֥וּ
יָדֶֽיךָ׃ יקוק ׀ יִמְלֹ֖ךְ לְעֹלָ֥ם וָעֶֽד׃ כִּ֣י
בָא֩ ס֨וּס פַּרְעֹ֜ה בְּרִכְבּ֤וֹ וּבְפָרָשָׁיו֙ בַּיָּ֔ם וַיָּ֧שֶׁב יקוק עֲלֵהֶ֖ם אֶת מֵ֣י
הַיָּ֑ם וּבְנֵ֧י יִשְׂרָאֵ֛ל הָלְכ֥וּ בַיַּבָּשָׁ֖ה בְּת֥וֹךְ הַיָּֽם
Then Moses and the Israelites sang this song to יקוק. They said: I will sing to יקוק, for He has triumphed gloriously; Horse and driver He has hurled into the sea. יקוק is my strength and might; He is become my deliverance. This is my God and I will enshrine Him; The God of my father’s [house], and I will exalt Him. יקוק, the Warrior— יקוק is His name! Pharaoh’s chariots and his army He has cast into the sea; And the pick of his officers Are drowned in the Sea of Reeds. The deeps covered them; They went down into the depths like a stone. Your right hand, יקוק, glorious in power, Your right hand, יקוק, shatters the foe! In Your great triumph You break Your opponents; You send forth Your fury, it consumes them like straw. At the blast of Your nostrils the waters piled up, The floods stood straight like a wall; The deeps froze in the heart of the sea. The foe said,“I will pursue, I will overtake, I will divide the spoil; My desire shall have its fill of them. I will bare my sword—My hand shall subdue them.” You made Your wind blow, the sea covered them; They sank like lead in the majestic waters. Who is like You, יקוק, among the celestials; Who is like You, majestic in holiness, Awesome in splendor, working wonders! You put out Your right hand, The earth swallowed them. In Your love You lead the people You redeemed; In Your strength You guide them to Your holy abode. The peoples hear, they tremble; Agony grips the dwellers in Philistia. Now are the clans of Edom dismayed; The tribes of Moab—trembling grips them; All the dwellers in Canaan are aghast. Terror and dread descend upon them; Through the might of Your arm they are still as stone—Till Your people cross over, יקוק, Till Your people cross whom You have ransomed. You will bring them and plant them in Your own mountain, The place You made to dwell in, יקוק, The sanctuary, O my lord, which Your hands established. יקוק will reign for ever and ever! For the horses of Pharaoh, with his chariots and riders, went into the sea; and יקוק turned back on them the waters of the sea; but the Israelites marched on dry ground in the midst of the sea.
This 30-line structure reminds us of God's splitting of the Sea with walls of water to the right and to the left and dry ground between them (Ex. 14:22).
(כב) וַיָּבֹ֧אוּ בְנֵֽי־יִשְׂרָאֵ֛ל בְּת֥וֹךְ הַיָּ֖ם בַּיַּבָּשָׁ֑ה וְהַמַּ֤יִם לָהֶם֙ חוֹמָ֔ה מִֽימִינָ֖ם וּמִשְּׂמֹאלָֽם׃
(22) and the Israelites went into the sea on dry ground, the waters forming a wall for them on their right and on their left.
As detailed in "Psalm 27: The Unique Case of Double Dots", Psalm 27 is connected to the Song of the Sea via similar themes in their initial verses and the special word לׅׄוּׅׄלֵׅ֗ׄאׅׄ in Psalm 27. The leading letters of the first four lines of the Song of the Sea as presented in the Torah read downward א-ל-ו-ל, the reverse of לוּלֵא. It is writing on the wall.
אָ֣ז יָשִֽׁיר־מֹשֶׁה֩ וּבְנֵ֨י יִשְׂרָאֵ֜ל אֶת הַשִּׁירָ֤ה הַזֹּאת֙ לַֽיקוק וַיֹּאמְר֖וּ
לֵאמֹ֑ר אָשִׁ֤ירָה לַֽיקוק כִּֽי גָאֹ֣ה גָּאָ֔ה ס֥וּס
וְרֹכְב֖וֹ רָמָ֥ה בַיָּֽם׃ עׇזִּ֤י וְזִמְרָת֙ יָ֔-הּ וַֽיְהִ לִ֖י
לִֽישׁוּעָ֑ה זֶ֤ה אֵ-לִי֙ וְאַנְוֵ֔הוּ אֱלֹקֵ֥י
אָבִ֖י וַאֲרֹמְמֶֽנְהוּ׃
(1) Then Moses and the Israelites sang this song to יקוק. They said: I will sing to יקוק, for He has triumphed gloriously; Horse and driver He has hurled into the sea. (2) יקוק is my strength and might; He is become my deliverance. This is my God and I will enshrine Him; The God of my father’s [house], and I will exalt Him.
As interesting as this is, there may be more writing on the wall. It just so "happens" (perhaps as Rashi explains Ex. 3:18), that the leading letters of the 15 "middle text bricks" (i.e., the middle section of text on 15 lines with two gaps) read downwards א-ז-מ-י-ת-ק-א-מ-נ-ש-א-ב-ת-י-ו.
This string of letters seems to pose a question: ?אָז מִי תָּקִא מִנְּשׂא בָּתָּיו. Why should such a string of letters have the potential to make any sense whatsoever?
The first word of the question is the first word of the first line of the Song of the Sea while the second word appears twice in the 16th line. The first two words of the question represent the first and second halves of the Song of the Sea, respectively (i.e., the entire Song of the Sea collectively).
The last three words of the question occur exactly once in the Tanakh, respectively:
(כה) וַתִּטְמָ֣א הָאָ֔רֶץ וָאֶפְקֹ֥ד עֲוֺנָ֖הּ עָלֶ֑יהָ וַתָּקִ֥א הָאָ֖רֶץ אֶת־יֹשְׁבֶֽיהָ׃
(25) Thus the land became defiled; and I called it to account for its iniquity, and the land spewed out its inhabitants.
(יג) וַיֹּ֥אמֶר קַ֖יִן אֶל־יקוק גָּד֥וֹל עֲוֺנִ֖י מִנְּשֹֽׂא׃
(13) Cain said to יקוק, “My punishment is too great to bear!
(יא) וַיִּתֵּ֣ן דָּוִ֣יד לִשְׁלֹמֹ֣ה בְנ֡וֹ אֶת־תַּבְנִ֣ית הָאוּלָם֩ וְֽאֶת־בָּ֨תָּ֜יו וְגַנְזַכָּ֧יו וַעֲלִיֹּתָ֛יו וַחֲדָרָ֥יו הַפְּנִימִ֖ים וּבֵ֥ית הַכַּפֹּֽרֶת׃
(11) David gave his son Solomon the plan of the porch and its houses, its storerooms and its upper chambers and inner chambers; and of the place of the Ark-cover;
Although the verb תָּקִא is used above in the third-person female (הָאָרֶץ) in the future tense (without the reversing וַ), it is also future tense for second-person male (c.f., future and past tenses in Lev. 18:28).
There are three plausible answers to this question: ?אָז מִי תָּקִא מִנְּשׂא בָּתָּיו. They depend on the interpretation of תָּקִא.
Interpreting תָּקִא in the second-person male future tense makes the question: Then whom will You (God) reject from raising his houses? This interpretation provides two of the three plausible answers. The two answers depend on the identity of whom/his.
Given the source of the last word בָּתָּיו, the first answer could be King David. God rejects King David as the builder of The Temple, in favor of his son, King Solomon (I Chron. 28:2-6).
(ב) וַיָּ֨קׇם דָּוִ֤יד הַמֶּ֙לֶךְ֙ עַל־רַגְלָ֔יו וַיֹּ֕אמֶר שְׁמָע֖וּנִי אַחַ֣י וְעַמִּ֑י אֲנִ֣י עִם־לְבָבִ֡י לִבְנוֹת֩ בֵּ֨ית מְנוּחָ֜ה לַאֲר֣וֹן בְּרִית־יְהֹוָ֗ה וְלַֽהֲדֹם֙ רַגְלֵ֣י אֱלֹהֵ֔ינוּ וַהֲכִינ֖וֹתִי לִבְנֽוֹת׃ (ג) וְהָֽאֱלֹהִים֙ אָ֣מַר לִ֔י לֹא־תִבְנֶ֥ה בַ֖יִת לִשְׁמִ֑י כִּ֣י אִ֧ישׁ מִלְחָמ֛וֹת אַ֖תָּה וְדָמִ֥ים שָׁפָֽכְתָּ׃ (ד) וַיִּבְחַ֡ר יְהֹוָ֣ה אֱלֹהֵי֩ יִשְׂרָאֵ֨ל בִּ֜י מִכֹּ֣ל בֵּית־אָבִ֗י לִהְי֨וֹת לְמֶ֤לֶךְ עַל־יִשְׂרָאֵל֙ לְעוֹלָ֔ם כִּ֤י בִֽיהוּדָה֙ בָּחַ֣ר לְנָגִ֔יד וּבְבֵ֥ית יְהוּדָ֖ה בֵּ֣ית אָבִ֑י וּבִבְנֵ֣י אָבִ֔י בִּ֣י רָצָ֔ה לְהַמְלִ֖יךְ עַל־כׇּל־יִשְׂרָאֵֽל׃ (ה) וּמִ֨כׇּל־בָּנַ֔י כִּ֚י רַבִּ֣ים בָּנִ֔ים נָ֥תַן לִ֖י יְהֹוָ֑ה וַיִּבְחַר֙ בִּשְׁלֹמֹ֣ה בְנִ֔י לָשֶׁ֗בֶת עַל־כִּסֵּ֛א מַלְכ֥וּת יְהֹוָ֖ה עַל־יִשְׂרָאֵֽל׃ (ו) וַיֹּ֣אמֶר לִ֔י שְׁלֹמֹ֣ה בִנְךָ֔ הוּא־יִבְנֶ֥ה בֵיתִ֖י וַחֲצֵרוֹתָ֑י כִּֽי־בָחַ֨רְתִּי ב֥וֹ לִי֙ לְבֵ֔ן וַאֲנִ֖י אֶהְיֶה־לּ֥וֹ לְאָֽב׃
(2) King David rose to his feet and said, “Hear me, my brothers, my people! I wanted to build a resting-place for the Ark of the Covenant of the LORD, for the footstool of our God, and I laid aside material for building. (3) But God said to me,‘You will not build a house for My name, for you are a man of battles and have shed blood.’ (4) The LORD God of Israel chose me of all my father’s house to be king over Israel forever. For He chose Judah to be ruler, and of the family of Judah, my father’s house; and of my father’s sons, He preferred to make me king over all Israel; (5) and of all my sons—for many are the sons the LORD gave me—He chose my son Solomon to sit on the throne of the kingdom of the LORD over Israel. (6) He said to me,‘It will be your son Solomon who will build My House and My courts, for I have chosen him to be a son to Me, and I will be a father to him.
Considering the first two words אָז מִי, the second answer could be closer to the Song of the Sea itself. The last word of the question בָּתָּיו may be an allusion to בָּתִּים in Ex. 1:21:
(כא) וַיְהִ֕י כִּֽי־יָרְא֥וּ הַֽמְיַלְּדֹ֖ת אֶת־הָאֱלֹהִ֑ים וַיַּ֥עַשׂ לָהֶ֖ם בָּתִּֽים׃
(21) And [God] established households for the midwives, because they feared God.
According to Rashi, the midwives who have בָּתִּים established by God are Jochebed (Shifrah) and Miriam (Puah), and בָּתִּים refers to the dynasties of priesthood and royalty descended from them, respectively. Given בָּתָּיו, all of this points to Moses and Aaron, sons of Jochebed and brothers to Miriam.
Moses and Aaron are later rejected by God from leading the Israelites into Israel (Num. 20:12):
(יב) וַיֹּ֣אמֶר יְהֹוָה֮ אֶל־מֹשֶׁ֣ה וְאֶֽל־אַהֲרֹן֒ יַ֚עַן לֹא־הֶאֱמַנְתֶּ֣ם בִּ֔י לְהַ֨קְדִּישֵׁ֔נִי לְעֵינֵ֖י בְּנֵ֣י יִשְׂרָאֵ֑ל לָכֵ֗ן לֹ֤א תָבִ֙יאוּ֙ אֶת־הַקָּהָ֣ל הַזֶּ֔ה אֶל־הָאָ֖רֶץ אֲשֶׁר־נָתַ֥תִּי לָהֶֽם׃
(12) But יהוה said to Moses and Aaron, “Because you did not trust Me enough to affirm My sanctity in the sight of the Israelite people, therefore you shall not lead this congregation into the land that I have given them.”
Thus, God rejects Moses and Aaron each from establishing his houses in Israel. The tribe of Levi does not receive a territorial inheritance.
(א) לֹֽא־יִ֠הְיֶ֠ה לַכֹּהֲנִ֨ים הַלְוִיִּ֜ם כׇּל־שֵׁ֧בֶט לֵוִ֛י חֵ֥לֶק וְנַחֲלָ֖ה עִם־יִשְׂרָאֵ֑ל אִשֵּׁ֧י יקוק וְנַחֲלָת֖וֹ יֹאכֵלֽוּן׃ (ב) וְנַחֲלָ֥ה לֹא־יִֽהְיֶה־לּ֖וֹ בְּקֶ֣רֶב אֶחָ֑יו יקוק ה֣וּא נַחֲלָת֔וֹ כַּאֲשֶׁ֖ר דִּבֶּר־לֽוֹ׃ {ס}
(1) The levitical priests, the whole tribe of Levi, shall have no territorial portion with Israel. They shall live only off יקוק’s offerings by fire as their portion, (2) and shall have no portion among their brother tribes: יקוק is their portion, as promised.
The third answer arises from interpreting תָּקִא in the third-person female future tense. The question becomes: Then whom will she reject from raising his houses?
This interpretation strongly suggests the Prophetess and Judge Deborah and Barak, son of Abinoam. Their account and Song is the Haftarah (for Ashkenazim) for Parashat Beshalach, which contains the Song of the Sea. Their initial encounter in Judges 4:4-9 appears surprisingly relevant.
(ד) וּדְבוֹרָה֙ אִשָּׁ֣ה נְבִיאָ֔ה אֵ֖שֶׁת לַפִּיד֑וֹת הִ֛יא שֹׁפְטָ֥ה אֶת־יִשְׂרָאֵ֖ל בָּעֵ֥ת הַהִֽיא׃ (ה) וְ֠הִ֠יא יוֹשֶׁ֨בֶת תַּחַת־תֹּ֜מֶר דְּבוֹרָ֗ה בֵּ֧ין הָרָמָ֛ה וּבֵ֥ין בֵּֽית־אֵ֖ל בְּהַ֣ר אֶפְרָ֑יִם וַיַּעֲל֥וּ אֵלֶ֛יהָ בְּנֵ֥י יִשְׂרָאֵ֖ל לַמִּשְׁפָּֽט׃ (ו) וַתִּשְׁלַ֗ח וַתִּקְרָא֙ לְבָרָ֣ק בֶּן־אֲבִינֹ֔עַם מִקֶּ֖דֶשׁ נַפְתָּלִ֑י וַתֹּ֨אמֶר אֵלָ֜יו הֲלֹ֥א צִוָּ֣ה ׀ יקוק אלקי־יִשְׂרָאֵ֗ל לֵ֤ךְ וּמָֽשַׁכְתָּ֙ בְּהַ֣ר תָּב֔וֹר וְלָקַחְתָּ֣ עִמְּךָ֗ עֲשֶׂ֤רֶת אֲלָפִים֙ אִ֔ישׁ מִבְּנֵ֥י נַפְתָּלִ֖י וּמִבְּנֵ֥י זְבֻלֽוּן׃ (ז) וּמָשַׁכְתִּ֨י אֵלֶ֜יךָ אֶל־נַ֣חַל קִישׁ֗וֹן אֶת־סִֽיסְרָא֙ שַׂר־צְבָ֣א יָבִ֔ין וְאֶת־רִכְבּ֖וֹ וְאֶת־הֲמוֹנ֑וֹ וּנְתַתִּ֖יהוּ בְּיָדֶֽךָ׃ (ח) וַיֹּ֤אמֶר אֵלֶ֙יהָ֙ בָּרָ֔ק אִם־תֵּלְכִ֥י עִמִּ֖י וְהָלָ֑כְתִּי וְאִם־לֹ֥א תֵֽלְכִ֛י עִמִּ֖י לֹ֥א אֵלֵֽךְ׃ (ט) וַתֹּ֜אמֶר הָלֹ֧ךְ אֵלֵ֣ךְ עִמָּ֗ךְ אֶ֚פֶס כִּי֩ לֹ֨א תִֽהְיֶ֜ה תִּֽפְאַרְתְּךָ֗ עַל־הַדֶּ֙רֶךְ֙ אֲשֶׁ֣ר אַתָּ֣ה הוֹלֵ֔ךְ כִּ֣י בְֽיַד־אִשָּׁ֔ה יִמְכֹּ֥ר יקוק אֶת־סִֽיסְרָ֑א וַתָּ֧קׇם דְּבוֹרָ֛ה וַתֵּ֥לֶךְ עִם־בָּרָ֖ק קֶֽדְשָׁה׃
(4) Deborah, wife of Lappidoth, was a prophet; she led Israel at that time. (5) She used to sit under the Palm of Deborah, between Ramah and Bethel in the hill country of Ephraim, and the Israelites would come to her for decisions. (6) She summoned Barak son of Abinoam, of Kedesh in Naphtali, and said to him, “The ETERNAL, the God of Israel, has commanded: Go, march up to Mount Tabor, and take with you ten thousand men of Naphtali and Zebulun. (7) And I will draw Sisera, Jabin’s army commander, with his chariots and his troops, toward you up to the Wadi Kishon; and I will deliver him into your hands.” (8) But Barak said to her, “If you will go with me, I will go; if not, I will not go.” (9) “Very well, I will go with you,” she answered. “However, there will be no glory for you in the course you are taking, for then GOD will deliver Sisera into the hands of a woman.” So Deborah went with Barak to Kedesh.
Deborah rejects (or delivers God's rejection of) Barak from achieving glory with 10,000 men from Naphtali and Zebulun, because he will not march up to Mt. Tabor without her. The two tribes led by Barak could be described by בָּתָּיו (his houses).
The Song of the Sea is not the only example in the Torah of added meaning through text structure and writing on the wall. Another example is found in Parashat Ha'Azinu (see "Ha'Azinu: Ascending and Descending").