Dina said she first dreamed of starting a band three years ago. In September, she and her sister Dareen, 19, who plays bass, teamed up with Lamia and Amjad, the keyboardist.

They were already iconoclasts: Dina and Dareen wear their hair teased into thick manes and have pierced eyebrows. During an interview at a Starbucks here, they wore black abayas  the flowing gown that is standard attire for women  but the gowns were open, showing their jeans and T-shirts, and their hair and faces were uncovered. Women are more apt to go uncovered in Jidda than in most other parts of the country, though it is still uncommon.

“People always stare at us,” Dareen said, giggling. She and her sister are also avid ice skaters, another unusual habit in Saudi Arabia’s desert.

The band gets together to practice every weekend at the sisters’ house, where their younger brother sometimes fills in on drums. In early November, Dina, who studies art at King Abdulaziz University, began writing a song based on one of her favorite paintings, “The Accolade,” by the English pre-Raphaelite painter Edmund Blair Leighton. The painting depicts a long-haired noblewoman knighting a young warrior with a sword.

“I liked the painting because it shows a woman who is satisfied with a man,” Dina said.

She had thought of writing a song based on “Last Supper” by Leonardo da Vinci but decided that doing so would be taking controversy too far. In Saudi Arabia, churches are not allowed, and Muslims who convert to Christianity can be executed.

Dina held out her cellphone to show a video of the band practicing at home. It looked like a garage-band jam session anywhere in the world, with the sisters hunching over their instruments, their brother blasting away at the drums and Lamia clutching a microphone.

“We’re looking for a drummer,” Lamia said. “Five guys have offered, but we really want the band to be all female.”