The emperor sprang to his feet at the sight of us. “Ah! Herr Mozart! Frau Mozart!” he called out. Beside him, Empress Maria Theresa gave us a warm smile.

“Your Majesties,” Papa said, bowing low to the ground. Of course he would do so, but the sight startled me—I had always seen my father with his head held high, the master of our household. It never occurred to me that he would behave differently in front of those with greater power.

Mama joined in with her curtsies, and Woferl and I followed their lead as we were each introduced to the emperor and the empress, then to their children.

It was only at the very bottom of my curtsy that I noticed the hooved shape of the emperor’s shoes. I blinked. When I looked again, they looked normal. My eyes darted to the rest of the audience. For an instant, I thought that one of the seated men appeared thin and willowy and blue.

I tried to get a better look, but then the emperor knelt to look at my brother. My attention shifted back to them. “And this! Ah!” the emperor said. “This boy must be the one we’ve heard so much about! How old are you, Herr Mozart?”

“Five years old, Your Majesty,” he said loudly. Though his skill was impressive enough, Papa had still instructed him to take two years off his age.

“Five!” the emperor said, rubbing his chin in mock wisdom. “I suppose you must be too small a boy to play the clavier, ja?”

At that, Woferl puffed up in defiance. “I am not, Your Majesty,” he declared. “I can reach all the keys, and if I stand I can reach the pedal, and I can play the violin as well.”

Behind him, the others in the audience chuckled. I caught the eye of the emperor’s smallest daughter, Princess Maria Antonia, who smiled at me. When her eyes darted to Woferl, she blushed and looked away.

The emperor let out a hearty laugh. “You all heard the boy. He can play the clavier! And the violin, as well!” Then he turned to me. “You must be Fräulein Mozart,” he said.

“Your Majesty,” I replied, sweeping into another deep curtsy.

“Lift your head, Fräulein, so that we may have a better look at you.”

I did so—and found myself staring straight into Hyacinth’s eyes.

I did not know what kept me from leaping away in shock, but there I stood, transfixed by the boy’s beautiful face. Did the others not see him? Here, he was no longer dressed in his assortment of leaves and shining twigs. Instead, his hair was pulled back into a low tail at the nape of his neck, tied with a neat length of white ribbon, and layers of trimmed lace adorned the breast of his shirt. The white-and-gold royal coat he wore made the tint of his skin appear even paler.

“Hello, Fräulein,” Hyacinth said, and the music of his voice was unmistakable. I turned my eyes down, terrified and elated to be the only one who might be seeing him. Above me came his chuckle.

“Herr Mozart,” he said to my father. “Are you sure your daughter is not an angel stolen from Heaven?”

Papa and Mama bowed their thanks. All they saw was the emperor. I said nothing as I curtsied again. My eyes flitted to my brother, but he had his back turned to me, his eyes already settled eagerly on the clavier. If he could see Hyacinth, he did not appear to notice him.

“We will hear young Herr Mozart first,” Hyacinth declared, then rose to his feet. I found myself turning to join my parents in the first row of audience seats, where my mother now sat beside the empress herself. I took my seat with them. My father remained standing, perhaps too anxious to sit, his eyes locked on Woferl as if there were no one else in the chamber. I pressed my hands into my lap.

Hyacinth had told me that the notebook would connect my world to his, and so I had written my music into it, on my secret page. I must have summoned him here.

Woferl struggled a bit to climb up onto the clavier bench, but once he was there, he needed nothing else. What did he see? I wondered. I kept my eyes on his bright red sleeves as he played. He added flourishes into his performance, and his fingers danced across the keys without effort, nimble and quick. In the corners of the chamber, a light mist had begun to build, gathering along the floor until it seemed as if we were shrouded in a dream.

My hands fidgeted endlessly in my lap, yearning to reach into my pocket for my pendant. I tried to predict how my own performance would go, whether I could bring the same wonder to my music as Woferl did to his. Would anyone want to hear me when my brother finished? Or would it be like my first song for Herr Schachtner, who had barely heard me at all? Would it please Hyacinth, to watch me perform? Had he come here to witness what I could do, so that he could begin his work on my wish? Was this a test of my talent for him to see if I was truly worthy?

Woferl played one piece, then another. Papa stepped up and covered the keys with a cloth, and Woferl continued to play as easily as before. Our audience gasped in delight.

Then, too soon, Woferl was finished, and suddenly all I heard around me were exclamations and applause, the clack of shoes as their owners rose to their feet. I joined in the clapping. Woferl hopped down from the bench and bowed low to his audience, then looked at me with a toothy grin. He hurried back to his chair. His eyes never went to the emperor—to Hyacinth—and I began to wonder if this time the princeling did not mean for my brother to see him. Perhaps he was only here for me.

My heart began to beat rapidly as the room’s attention shifted to me. The emperor nodded for me to step forward. “Fräulein Mozart,” he said.

I rose from my chair in a daze and walked to the clavier. There, I took my position on the bench and rested my hands against the keys. I’d memorized my music in those long morning practices and late-night lessons. It was easier this way to see the notes how I wanted to see them, without the papers in front of me. But here, with the phantom mist curling against my feet, I became unsure that I could see anything. The fog seemed to touch the edges of my mind, softening my nerves until I felt like I was not a part of my body at all. Until the world around me looked like a dream.

In the corner of the room, the princeling sat in the emperor’s chair and watched me with a curious tilt to his head.

My breath seemed to hang in the air. I reached for the still-ness in my mind. My fingers curled against the keys and I began to play.

The notes that emerged from the clavier did not seem like music of the real world, what my menuetts were when I practiced them at home. Instead, they sounded like what I’d heard in the hidden grotto, like the voice of Hyacinth on the wind, suspended on the breeze. They sounded like they did in my head, perfect and fully formed, the same way they seemed right before they usually emerged into the world flawed and distorted. I floated above myself as I played, immersed in the dream of it, intoxicated, unwilling to leave.

I was not playing for an audience. I was playing for myself. And slowly, gradually, the chamber around me began to change.

The marble pillars turned wooden. Leaves budded from the stems of the chandeliers and candle sconces. Ivy crawled along the spectators’ chairs, their tendrils spiraling in long, tight patterns around the legs, winding their way across the floor until they reached my clavier. The light filtering through the windows dimmed, turned cool and blue. The mist thickened, mixing with the sound of notes in the air. My hands numbed, moving seemingly of their own accord. My body leaned into the music, swayed by the sound.