Edwards died last week at age 91.
Berry Gordy clasped hands with Smokey Robinson and organ music played as they entered the Bethel AME Church in Detroit Wednesday morning.
Stevie Wonder, who also signed to Motown, is expected to make a musical tribute at the ceremony.
Edwards stayed behind when Motown Records moved to California. She amassed memorabilia and preserved the old Detroit headquarters, Hitsville U.S.A., turning it into a museum that opened in 1985.
Berry Gordy has said his sister "protected the Motown legacy for generations to come."