Gladys, a friend of the late singer, started the tribute with a beautiful rendition of "Amazing Grace" ... bringing the audience to its feet one last time at the end of the 3-hour award show.

Gladys introduced Donnie McClurkin, and he energized the room by singing "Climbing Higher Mountains."

A gospel choir came onstage for CeCe Winans' performance of "Mary Don't You Weep" ... and people were dancing in the aisles by the time Ledisi launched into "How I Got Over."

The memorial performance ended with gospel duo Mary Mary singing a traditional gospel, "Old Landmark."

Aretha died August 16 after a long battle with pancreatic cancer. She was 76.