“I feel that it’s important that I start shaping my legacy and doing things that have a little more substance,” Beyonce says.

“I want people to think when they listen to my music. I want it to help them through their painful memories, their painful moments, their most happy moments. I want it to bring out that happiness.”

Not that the pop superstar should worry about her mark on the music world. She has sold in excess of 75 million albums and, in the process, has become one of the highest-selling singers ever.

After a year off work, Beyonce is well and truly back with her new album, 4, and a headline performance tonight at the Glastonbury music festival in the UK.

She’ll also spend the coming months heavily promoting 4.

Behind the scenes, Beyonce says she has found an inner peace, relishing the fact that time out has helped establish a better perspective on work and life.

A self-confessed workaholic, Beyonce enjoyed not being on the clock, setting her own schedule.

“Taking time off was probably the best year of my life. I never thought I would say that because I love my job and I still worked. I can’t help myself. I recorded 70 songs for my album but I did it on my own time.

“I didn’t have any labels or any human telling me what I should be doing,” she says.

“I was able to spend time with my family and pick my nephew up from school and sleep in my bed. I’m so happy I’ve done it and now I’ve learned that it’s just necessary to have that time to yourself.

“I am hopefully going to continue to have the balance.”

Starting as one third of the hugely successful girl group Destiny’s Child, Beyonce has come a long way. She has 16 Grammy Awards to her name, with solo hits including Single Ladies, Halo and If I Were A Boy.

She rarely talks about her husband, Jay-Z, but admits he had something to do with selecting the album title, 4.

“Well, 4 is definitely the title because it’s my fourth (solo) album,” she explains.

“Also because it’s been my favourite number since I was a kid. I was married on April 4, I was born on September 4, my husband was born on December 4, my mother was born on January 4.

“I’ve won a lot of money with the number 4 while gambling, which I don’t do often, but it’s just a really lucky number for me.

“Since this is the most personal album, I figured it was time to name it my favourite number.”

While some may dismiss Beyonce as a pop star, she takes her job extremely seriously.

And she’s determined to continue speaking for her fans, many of them female.

“I feel like my voice is way deeper than I could ever have imagined,” she says.

“When I had women coming up to me saying, ‘You know, I had to sneak to listen to your music, but it makes me feel strong and now I’m saving up my money and I’m moving away from here’, it makes me feel like my purpose is so much deeper, so I’m gonna continue to write those songs that give women strength.”

Predictable is not a word Beyonce wants used to describe her or her music. She wants to keep raising the bar.

“I feel like if people can predict your next move, it’s just not interesting,” she says. “And I’ll be bored, and if I’m bored then everyone else is bored.”

Beyonce has enjoyed so much success she could have retired long ago but, refreshingly, she is driven to create new sounds, to up the ante, and has no inclination towards complacency.

“I always want to challenge the music industry,” she says. “I feel like it’s kinda my job to create the new up-tempos, it’s kinda my job to set the tone and to be the example.

“It’s sometimes risky but it’s the only reason I’ve been able to last as long as I have in this industry because it’s really short-lived.”

And despite all her experience, Beyonce admits she still gets the jitters performing.

“I always want to have that nervous ball in my stomach before I go on stage. That’s how I know I’m doing the right job and it’s something still exciting for me,” she says.

Beyonce taking to the stage at Glastonbury today, sharing the bill with U2, Queens of the Stone Age, the Kaiser Chiefs and Coldplay, is a perfect example of how she continues testing herself.

“Glastonbury is a life-long dream,” she says. “There aren’t that many pop artists that close Glastonbury, and I almost feel that I am unworthy.

“It feels good that I can still feel so out of my element. I hope it rains. I want it muddy. I want to make sure I deliver and I’m gonna give 100 per cent and I’m sure it will be one of those memories that I take with me to my grave.”