People Watching is the title single from the North Shields singer's upcoming third album.
His previous albums, 2019's Hypersonic Missiles and Seventeen Going Under, released in 2021 topped the UK charts, with the second shortlisted for the Mercury Prize.
Sam said Annie was the person who gave him the confidence to get up on stage but told Radio 1 "she was always like, 'why haven't you mentioned us in your acceptance speech?
"I taught you everything.
"She always used to guilt trip us about it."
In the single, Sam sings about promising to get Annie out of the care home where she died, which he describes as "falling to bits and understaffed".
He said he was with Annie when she died, a moment referenced in the song with the line: "I stayed all night till you left this life cos that's just love."
He told Radio 1: "It’s just a song about how much I love her really and how much I respected her.
"She was larger than life, so I felt like she needed something that was soaring."
Sam said People Watching was the last song he wrote for the album.
Around the time of Annie's death, he says he was finishing up the album but then "wrote a load of new songs", including the new single.
"It ended up being one of the most euphoric tracks on the album, I think," he says.
"It made sense, it's about Annie."
He says the album, set to be released in full in February, is "more outward-pointing than Seventeen Going Under was," describing it as "a collection of stories".
"It's about people I know and my hometown and [People Watching] felt like a great title."
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