Tom Hanks, Jay Leno and Stevie Wonder were among those who helped celebrate the life of Michael Clarke Duncan during a memorial service.

The nearly four-hour service in Los Angeles was marked by speeches, rousing gospel performances and photos of the always-smiling star of The Green Mile.

Hanks and talk show host Leno shared stories about the star and actress Holly Robinson Peete talked about meeting Duncan while he was still a celebrity bodyguard.

Wonder appeared via video, solemnly playing piano and singing the opening verses of his life-affirming song As for the man he called "a gentle giant".

Duncan died on September 3 at 54, having never fully recovered from a heart attack in July. His doctor was among the speakers at the service at Forest Lawn Memorial Parks and Mortuaries in Los Angeles.

Former reality TV star the Rev Omarosa Manigault, who was Duncan's fiancee, also attended along with Duncan's mother, sister and nephews.

Backed by a gospel choir, singers Angie Stone, Kelly Price, Kenny Lattimore and Abraham McDonald lent their voices to the private funeral. State Assemblyman Mike Davis and Los Angeles City Council President Herb Wesson also attended, with the council declaring Monday as "Michael Clarke Duncan Day".

Leno said he was touched by the actor's positivity and lack of cynicism. "Just to see such a pure heart and pure kindness, and to see it taken so early," the comedian said, his voice cracking. "There are no sadder words than what might have been."

Other speakers included actors David Boreanaz and Geoff Stults, and Bones creator Hart Hanson.