“I get a big lump in my throat when I try to sing one of our songs right now,” she said.

She’ll get a little help next week as Usher is set to sing from the Ashford & Simpson catalog for what promises to be a poignant moment in the usually upbeat Grammy nominations prime-time special. It will be part of a joint tribute to Ashford and Jerry Leiber, and will also feature Mike Stoller, who was Leiber’s longtime writing partner.

Leiber and Stoller wrote classics such as “Hound Dog,” ‘‘Jailhouse Rock,” ‘‘Yakety Yak” and other hit songs that came to define early rock ‘n’ roll. Ashford and Simpson helped define the Motown sound with hits like “Ain’t No Mountain High Enough,” ‘‘Reach Out and Touch Somebody’s Hand” and “You’re All I Need to Get By,” as well as soul hits for themselves and others.

“I knew both Jerry Leiber and Nick very well,” said Ken Ehrlich, producer of the nominations special and the Grammy broadcast, on Monday. “It was pretty rough for me in August when they both passed away. … We lost two of the greatest songwriters of the formative rock and R&B era.”

The tribute will be a change in tone for the fourth annual special, to air live from the Nokia Theatre in Los Angeles on CBS on Nov. 30. The one-hour special in past years usually focused on select nominations and performances from those likely to get those bids. Rihanna, Katy Perry, The Band Perry, Sugarland and Lady Gaga are among those scheduled to participate.

But Ehrlich didn’t want to wait until the Feb. 12 Grammy broadcast to honor the lost legends.

“It felt to me like it might be appropriate to do it at the end of the year, closer to the time of their passing,” he said.

The segment will feature both Simpson and Stoller on separate pianos, as Usher sings. Simpson says she might join in when Usher sings one of their songs, which she expects to be “You’re All I Need to Get By,” but she’s happy not to be doing most of the singing.

“It certainly would make it a lot easier,” she said of Usher performing. “I will be very happy to lean on him.”

She called the death of her husband, with whom she had two daughters, “the most difficult thing I’ve had to do in my life.”

Simpson said his illness came quickly. “Nobody ever really thought of him being sick, and he really wasn’t until the very end,” she said.

The pair were married for 36 years. She said she still goes to their New York City restaurant and club, the Sugar Bar, where they nurtured upcoming talent over the years, and doesn’t rule out writing music on her own.

“I figure the residue of what he leaves here will give me something to carry on with,” she said. “I expect he’ll be whispering in my ear and pointing me in a direction that is right, in time.”