Agatha and Margaret in the Kingdom of Music

In case you don't yet know them, Margaret and Agatha are two little twin sisters. Well, not so little, actually. They can already walk and talk. And what they love most of all is exploring the big, wide world.

Today their mother has taken them to visit their grandfather. Grandpa works in a big building full of music. It's called the Concert Hall. Agatha and Margaret were very excited to be going there, because they really liked music.

"Hello, Grandpa," the twins said as soon as they arrived.

"Hello, my beautiful granddaughters. My, how you've grown!" he exclaimed. The twins stretched their hands as high as they could above their heads to help Grandpa see just how tall they were now.

"Come on in, I'm going to show you many wondrous things today," Grandpa said, taking their hands. Margaret and Agatha waved to their mother, who was off to do some shopping and would pick them up again at lunchtime.

The twins and their grandfather walked down a long corridor lined with mysterious doors. "Grandpa, what's behind that door?" asked Agatha.

"That's where our musician friends hide their instruments away," Grandpa explained.

"What are musicians?" Margaret asked, twizzling a loose lock of hair around her finger.

"They're people who make music," Grandpa laughed.

"And what are instruments?" Agatha asked.

"Oh, they are magical things that can produce wonderful sounds. And when you put the sounds together, they make songs."

"Songs? I know some songs!" Agatha exclaimed happily, and began to sing. "Baa, baa, black sheep…"

“…and one for the little boy who lives down the lane," Margaret joined in.

"You two sing beautifully," said Grandpa. "You know what? Let’s go in here and have a look at something." He opened the nearest door and flicked…