Psalms 65 - 78

The "Lord" or "God" as referred to many times by David, as Jehovah. David said -

"That men may know that thou, whose name alone is JEHOVAH, art the most high over all the earth" (Old Testament Psalms 83:18)

or also -

"...by his name JAH... " (Old Testament Psalms 68:4)

While in the Kirtland Temple, the Prophet Joseph Smith and Oliver Cowdery testified -

"THE veil was taken from our minds, and the eyes of our understanding were opened.
2 We saw the Lord standing upon the breastwork of the pulpit, before us; and under his feet was a paved work of pure gold, in color like amber.
3 His eyes were as a flame of fire; the hair of his head was white like the pure snow; his countenance shone above the brightness of the sun; and his voice was as the sound of the rushing of great waters, even the voice of Jehovah, saying:
4 I am the first and the last; I am he who liveth, I am he who was slain; I am your advocate with the Father." (Doctrine and Covenants Section 110:1 - 4)

With these verses, it is clear whom Jehovah of the old Testament is. Jesus Christ who is our Redeemer, is referred to in many of the songs in the Psalms -

"Let the words of my mouth, and the meditation of my heart, be acceptable in thy sight, O LORD, my strength, and my redeemer." (Old Testament Psalms 19:14)

"And they remembered that God was their rock, and the high God their redeemer." (Old Testament Psalms 78:35)

"I will walk in mine integrity: redeem me, and be merciful unto me." (Old Testament Psalms 26:11)

"...Arise for our help, and redeem us for thy mercies' sake." (Old Testament Psalms 44:26)

"...But God will redeem my soul from the power of the grave: for he shall receive me." (Old Testament Psalms 49:15)

"...Draw nigh unto my soul, and redeem it..." (Old Testament Psalms 69:18)

"He shall spare the poor and needy, and shall save the souls of the needy.
14 He shall redeem their soul from deceit and violence..." (Old Testament Psalms 72:13 - 14)

And also -

"...he shall redeem Israel from all his iniquities" (Old Testament Psalms 130:8)

Redeem means -

- to free from the consequences of sin, to atone for, to expiate (Merriam Webster Dictionary)

Jesus Christ is our Savior and Redeemer as Amulek teaches -

"And he shall come into the world to redeem his people; and he shall take upon him the transgressions of those who believe on his name; and these are they that shall have eternal life, and salvation cometh to none else." (Book of Mormon Alma 11:40)