The Shake It Off singer hit headlines across the globe when she wrote an open letter to the firm accusing bosses of short-changing artists by refusing to pay royalties during a three-month free trial period for subscribers.

Apple chiefs later reversed their decision in a landmark victory for Swift, and the pop star has now revealed she wrote the letter in the middle of the night and turned to her mother, Andrea Finlay, for advice before she published it.

She tells Vanity Fair magazine, "I wrote the letter at around 4am. The (Apple) contracts had just gone out to my friends, and one of them sent me a screenshot of one of them. I read the term 'zero per cent compensation to rights holders'. Sometimes I'll wake up in the middle of the night and I'll write a song and I can't sleep until I finish it, and it was like that with the letter... (I feared) people would say, 'Why won't she shut up about this?'... My fears were that I would be looked at as someone who just whines and rants about this thing that no one else is really ranting about... I read it (the letter) to my mom. She's always going to be the one. I just said, 'I'm really scared of this letter, but I had to write it. I might not post it, but I had to say it'."

Swift goes on to praise Apple chiefs for taking onboard her criticism and being brave enough to change their policy, adding, "Apple treated me like I was a voice of a creative community they actually cared about..."