Radak: Refer to 78:1:2:1.

Malbim: The author strengthens Malchus Beis David and the Beis ha'Mikdash that he built, against Malchus Efrayim and the Mishkan, which was in Efrayim's portion - "va'Yim'as b'Ohel Yosef uv'Shevet Efrayim Lo Vachar" (verse 67). It tells all that happened to Yisrael from when they left Egypt until David ruled. Even though the generations angered Hashem, Hashem knew that will rise a Dor like His heart; they will fear and take Musar. Also, a king will rise - he and the Mikdash that he will build will be a path of general perfection, and fixing the ruin of previous generations. This is the purpose and hope of coming generations until the deadline [for the redemption].

Radak: "Torasi" - I tell the benefits that Hashem did for Yisrael. From my words You will learn to fear him, and not rebel against His word and Mitzvos.

Malbim: This Shir will tell the events of the Avos simply. However, the events of Yisrael are unlike those of other nations. All that happened to Am Hashem was with Hashgachah Peratis and Hashem's miracles. Knowing the events is Torah and Emunah! From them are known Hashem's existence, ability, Hashgachah, reward and punishment. Therefore, it says Ha'azinah Torasi.

Malbim: The external of the story is Imrei Fi. With the internal, the Torah imbued in it, they are intertwined.