Adam Schlesinger, from the US power pop band Fountains of Wayne, has died aged 52 in a New York hospital, his family lawyer has confirmed.
He had been receiving treatment for Covid-19, with the use of a ventilator.
The bass player co-wrote the band's 2003 hit, Stacy's Mom - an ode to unrequited teenage lust, which starred model Rachel Hunter in the video.
He went on to win Emmy and Grammy awards for his soundtrack work on Crazy Ex Girlfriend, and A Colbert Christmas.
Chris Carrabba, from the band Dashboard Confessional, confirmed his death.
"I am grasping for the right words" he tweeted. "My dear friend Adam Schlesinger has passed away from COVID-19."
He added: "I knew him best as a mentor, and a friend. We must take this seriously. People are sick and dying. It is hard to stay locked indoors but lives will be saved. Take care of each other. Rest In Peace, my dear friend."
I am grasping for the right words. My dear friend Adam Schlesinger has passed away from COVID-19. You know him best through his music. From his band @fountainsofwayn to the countless movies and tv shows he scored, most recently My Crazy Ex Girlfriend (cont’d) pic.twitter.com/to8H4IoLtj— Dashboard Confessional (@dashboardmusic) April 1, 2020
The death toll from the coronavirus pandemic in the US has gone above 5,000, while confirmed cases worldwide are close to reaching one million.
Hollywood actor and director Tom Hanks recently recovered from the virus. In 1997, Schlesinger received an Oscar nomination for writing the title track for That Thing You Do!, the 1997 musical comedy directed by Hanks.
"He was a One-der," wrote Hanks, referencing the film's fictional band The Wonders, who enjoyed success with the title track. "Lost him to Covid-19. Terribly sad today. Hanx."
There would be no Playtone without Adam Schlesinger, without his That Thing You Do! He was a One-der. Lost him to Covid-19. Terribly sad today. Hanx— Tom Hanks (@tomhanks) April 2, 2020
DJ and producer Mark Ronson also paid tribute on Thursday to the "brilliant" musician, pointing to his "gem" of a track from the same movie.
Schlesinger's current bandmate, Reni Lane, from their synth-pop duo Fever High, added she felt "incredibly lucky" to have known him.
"I feel incredibly lucky to have been part of his life in some way and I will never forget all that I learned from him," she posted on her Instagram story.
"My heart goes out to his family, friends and everyone who was touched by his music."
Fountains of Wayne formed in New York in 1995 but rose to prominence in the UK in 2003 with Stacy's Mom, which peaked at number 11.
The track became an instant cult classic among adolescents owing to its catchy hormone-driven chorus, and accompanying video featuring Hunter - poolside in a bikini - in the titular role.
It also got them Grammy nominations for best pop performance and best new artist.
They put out five albums, with the last one, Sky Full of Holes, coming in 2011.
Alongside his work with the band, and other acts Ivy, and Tinted Windows, Schlesinger scored countless movies and made many TV soundtracks.
His music for the Broadway adaptation of the movie Cry-Baby received a Tony Awards nomination in 2008.
And he won a Grammy in 2009 for best comedy album, for his efforts on A Colbert Christmas: The Greatest Gift Of All!, by the US chat show host.
At the 2019 Emmys, he won the award for outstanding original music and lyrics for the track Antidepressants Are So Not A Big Deal, from Crazy Ex Girlfriend.
Aline Brosh McKenna, who co-created the TV musical comedy-drama, paid tribute, saying she had known Schlesinger since the early 1990s.
"Adam was so funny, so kind, so opinionated, so clever, so passionate," she wrote.
"We worked together and agreed and disagreed and rejoiced and bemoaned and celebrated and it felt extra sweet for me because I'd known him so long.
"I love that guy. I love all the memories."
Schlesinger was married to Katherine Michel from 1999-2013 and he is survived by their two daughters, Sadie and Claire.