What got you started?

Katia: Listening to my mother – she was a pianist and piano teacher.

Marielle: Watching Katia give her first concert, when she was seven and I was four. I sat in the audience and said: "I want to do that, too."

What was your big breakthrough?

K: Winning a national competition for young musicians when I was seven. The prize was to perform a Mozart concerto with orchestra at the Théâtre des Champs-Elysées in Paris. I knew then I would be a pianist all my life.

M: Recording Gershwin's Rhapsody in Blue with Katia in 1980. It brought us a big audience.

Who or what have you sacrificed for your art?

K: Nothing at all. My art gives me everything; in exchange, I give it everything I have.

M: Nothing. I haven't had a family, but it hasn't felt like a sacrifice. I love my freedom too much.

What piece of music would feature on the soundtrack to your life?

K: Rhapsody in Blue. I love the way it combines lyricism with a sense of reason.

M: Ravel's Mother Goose. He was born on the Basque coast of France, like us.

Do you suffer for your art?

K: Yes, physically. I'm small and thin, and the hours of practice are exhausting for my body. It's like being a dancer.

Which living artist do you most admire?

K: Daniel Day-Lewis. His voice is like pure music.

M: [The musician] Robert D Levin. He has such an amazing knowledge of music.

Is working as a duo difficult?

K: Yes and no. It's difficult to keep piano duets from sounding mechanical. But I love working with my sister.

M: Music itself is difficult, whether you're a duo or not.

Complete this sentence: At heart I'm just a frustrated . . .

K: Rock'n'roll guitarist.

M: Swimmer.

Is there an art form you don't relate to?

K: A certain kind of French theatre, in which everyone talks too much.

What's the best advice anyone ever gave you?

K: Miles Davis taught me to understand the relationship between music and silence.

M: The best advice comes from my sister, every day.

In short

Born: 1950 (Katia) and 1952 (Marielle); Bayonne, France.

Career: Have performed together since they were children, and will play in Proms 32 (9 August) and 43 (17 August) at the Royal Albert Hall, London (box office: 0845 401 5040).

High point: Katia: "Establishing our own record company."

Low point: Marielle: "Listening again to recordings we did as teenagers."