All 2021 Academy Awards nominees for Best Original Song will be performed during the preshow, which begins at 6:30 p.m. ET — not during the main show, which begins 90 minutes later.

The pre-show and main ceremony will be broadcast on ABC, as well as available to stream on Hulu Live TV, YouTubeTV, AT&T TV, FuboTV and on ABC.com (with provider authentication). The awards for Best Song and Best Score will be given out during the main show.

Leslie Odom Jr., a double nominee for acting and songwriting for “One Night in Miami,” will perform the end-titles theme he co-penned for the film, “Speak Now.” Diane Warren and singer Laura Pausini will join forces again for “Io Si (Seen),” which they co-wrote for “The Life Ahead.” “Fight for You” will be performed by the singer/co-writer H.E.R., who performed the old-school-soul throwback anthem over the end credits for “Judas and the Black Messiah.” “Hear My Voice,” the closing theme from “The Trial of the Chicago 7,” will see Celeste joined by the film’s composer and her co-writer on the song, Daniel Pemberton.

Four of the five performances weree pre-recorded on the Dolby Family Terrace of the Academy Museum of Motion Pictures, with the fifth being filmed in Húsavík, Iceland — the last of those being, of course, the nominee that is actually titled “Húsavík,” from the film “Eurovision: The Story of Fire Saga.”

The main motivation for airing the performances during the pre-show was to give them each equal time, although lowering the air time of the main show — which regularly goes beyond its three-hour time — was part of the plan as well.

Oscar veteran Jesse Collins, who is producing the show with Steven Soderbergh and Stacey Sher, explained how the Best Song performances will work during an interview with Variety last week that also featured Oscar musical director Questlove.

“Instead of picking out two or three of the songs or turning it into some kind of mega-mix medley, we’re able to do full performances — you get the entire song,” Collins said. “We’ll build the creative [treatment of the performance], pre-tape it and shoot it in a Covid-safe yet entertaining way, and before that performance, [the artist] will do an interview where we’ll talk about the song, and then throw to the performance.”

During the main show, Questlove will serve in the role normally performed by the orchestra, DJ-ing music that was recorded specifically for the show by his group, the Roots. “I’m handling pretty much all of the musical elements — the production, including the scoring of original music, and as DJ, I will be the lone orchestra,” he told Variety last week. “The Roots [recorded] all of the musical cues [for the show] ahead of time, like a month ago. We knocked out about 50 or 60 musical cues, and I will DJ those songs from the stage.”

He promised that the music will highlight the work of many great Hollywood film composers. “Everyone knows John Williams because he did ‘Indiana Jones’ and ‘Star Wars’ and all that stuff,” Questlove said. “But there’s a whole slew of people like Peter Thomas [Edgar Wallace films], Lalo Schifrin [‘Mission Impossible,’ ‘Dirty Harry’], Bill Conti [‘Rocky,’ ‘The Right Stuff’], Keith Mansfield [‘Loot,’ ‘Taste of Excitement’], Piero Piccioni [‘Swept Away’] — names that most people don’t necessarily know, but people who stay for the credits do, like I did when I was kid. I want to make sure they’re included too. In those 60 songs we recorded, we covered some classic, classic composers from Hollywood and across the world.”

He added, “A lot of hip-hop heads will be like, ‘Wait, I know that sample!’ They’ll realize that half of the hip-hop catalog that we’ve fallen in love with comes from library music scores of these composers from the ‘50s, ‘60s and ‘70s.”

The 2021 Academy Awards pre-show airs on ABC at 6:30 p.m. ET, with the main show following at 8 p.m. ET.