Guðnadóttir, who also won the Original Score prizes at the Baftas and Golden Globes, said it had been "an honour" to get to know the work of the other nominees.
"A film composer is only as creative as the dialogue with the director," she said. "Todd Phillips was so generous to invite me on this journey."
She continued: "My family, my beautiful family are here with me tonight, my incredible husband Sam – my other set of ears; to my mother and my son..."
She concluded: "To the women, to the mothers, to the daughters, who hear the music bubbling within, please speak up. We need to hear your voices."
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