Shane Baker, who has sung with Marie on her solo tour, will perform duets with her "until further notice" or until doctors clear Donny Osmond to resume singing, an Osmond spokesman told the Las Vegas Sun.
A singer and producer based in the country music center of Muscle Shoals, Ala., Baker is the son of well-known country music songwriter and producer Gary Baker, who has been in Marie's band in past years.
Donny Osmond missed his first show March 18. Marie performed on her own before arranging for Baker to join her.
Ticket-holding fans insisting on seeing Donny and Marie together in their resident production at the Flamingo Showroom can contact the Flamingo box office for refunds, the Sun said.