Revelation 14

In the 5th chapter of Revelations we read that many in the pre-mortal existence as the "Lamb" had taken the book from Him who sat on the throne -

"...they sung a new song, saying, Thou art worthy to take the book, and to open the seals thereof: for thou wast slain, and hast redeemed us to God by thy blood out of every kindred, and tongue, and people, and nation;
10 And hast made us unto our God kings and priests: and we shall reign on the earth." (New Testament | Revelation 5:9 - 10)

And again, as the Lamb stood on mount Sion, those that would be kings and priests on a celestialized earth -

"...they sung as it were a new song before the throne..." (New Testament | Revelation 14:3)

I am sure it was a "song of redeeming love" for -

"These were redeemed from among men, being the firstfruits unto God and to the Lamb." (New Testament | Revelation 14:4)

In modern revelation, we learn more -

"...with the voice together sing this new song, saying:
99 The Lord hath brought again Zion;
The Lord hath redeemed his people, Israel,
According to the election of grace,
Which was brought to pass by the faith
And covenant of their fathers.
100 The Lord hath redeemed his people;
And Satan is bound and time is no longer.
The Lord hath gathered all things in one.
The Lord hath brought down Zion from above.
The Lord hath brought up Zion from beneath.
101 The earth hath travailed and brought forth her strength;
And truth is established in her bowels;
And the heavens have smiled upon her;
And she is clothed with the glory of her God;
For he stands in the midst of his people.
102 Glory, and honor, and power, and might,
Be ascribed to our God; for he is full of mercy,
Justice, grace and truth, and peace,
Forever and ever, Amen." (Doctrine and Covenants | Section 84:98 - 102)

We learn more of these "kings and priests" who would reign on the earth as John -

"...saw as it were a sea of glass mingled with fire: and them that had gotten the victory over the beast, and over his image, and over his mark, and over the number of his name, stand on the sea of glass, having the harps of God.
3 And they sing the song of Moses the servant of God, and the song of the Lamb, saying, Great and marvellous are thy works, Lord God Almighty; just and true are thy ways, thou King of saints." (New Testament | Revelation 15:2 - 3)

I believe this new song sung by Moses, the Lamb, and of the righteous and exalted saints is the "song of redeeming love".