The Ostrev facility was on the northern face of Tier Four, built into the side of one of the Spire's great structural pillars — the massive load-bearing columns, sixty meters in diameter, that ran from the city's foundation plates all the way up to the Upper Rings. The pillar's exterior had been sheathed in photoreactive panels sometime in the last decade, giving it a shifting iridescence that was probably impressive from the outside of the city but from where Kael stood — inside the Tier, looking across the transit corridor toward the pillar's service entrance — mostly just lit up the condensation on the ceiling ducts in colors that had no business being here.
The access code Rennick's people had sent him worked on the first try. The service door opened into a utility corridor, then a second door with a second code, then a stairwell that went down rather than up — which meant the facility was in a sub-level, carved into the pillar's interior. The acoustics changed immediately: the ambient noise of Tier Four's transit corridors, the hum of generators and ventilation and the constant low vibration of a city that never entirely stopped moving, fell away and was replaced by something cleaner. Engineered silence. The kind that cost money.
The training space was about twenty meters square. The walls, floor, and ceiling were all lined with resonance-treating material — the advanced kind, not the cheap foam-block type Kael had seen in Pit prep rooms, but layered composite panels that could be adjusted to absorb or reflect specific frequencies depending on what the training session required. There were adjustable baffles in the ceiling, a full-spectrum output scanner on the east wall, and a rack of training equipment along the south side: impact targets, resonance-discharge panels calibrated to different resistance ratings, and several instruments in sealed cases whose contents Kael did not immediately investigate because he had been trained, by experience rather than instruction, not to touch things that weren't specifically his to touch.
There was also a person already there.
She was sitting cross-legged in the center of the floor with a keyboard in her lap. Not a performance keyboard — a training model, flat and unpowered, the kind used for finger exercises and chord practice. She was running her right hand through something complex, a rapid series of chord changes at the top of the register, while her left hand sat motionless on her leg. She had her eyes closed.
She was, Kael estimated, about seventeen. She had the stillness of a Harmonist in focus — that particular quality of being completely concentrated on something invisible, the way a Harmonist's power operated, building resonance not through visible action but through sustained, invisible frequency. The tessaviol on the floor beside her was a better instrument than Joss's by several orders of magnitude — full acoustic body, resonance cell built into the neck, the kind of piece that had a workshop name on it.
He had apparently been sent to a training space that already had an occupant.
He considered backing out of the room and messaging Rennick for clarification. While he was considering this, the girl opened her eyes.
They were dark brown and currently expressing the particular irritation of someone whose concentration had just been interrupted.
"You're Rennick's new fighter," she said. It was not a question.
"I didn't know the space was occupied."
"It usually isn't. I had an early session." She looked at him with the frank assessment of someone accustomed to evaluating quickly. "Kael Voss. Won Slot Seven at the Pit last night against a Dissonant."
"Word travels."
"Rennick talks about fighters the way other people talk about equipment. Which is to say factually and without much personal detail." She set the training keyboard aside and stood. She was tall — almost as tall as him — and moved with the precise economy of someone who had been trained to be aware of their own body in space. "I'm Sera Ondas. I use the space on even-cycle mornings. If you're going to be here regularly, we should work out a schedule."
"Rennick said three days a week. He didn't specify times."
"Then you should specify times with him before we end up here at the same time again." She picked up the tessaviol and clipped it to her jacket. "Are you staying? I have twenty minutes left in my session if you want to work around each other."
Kael looked at the training space. Twenty meters square, resonance-treated walls, calibrated equipment. He had three days a week in here. He had been working on rooftops for three years.
"I'll stay," he said.
He set up in the corner farthest from her and went through his warmup sequence, the physical mechanics first, the way Seren's interview said. Rod articulation, strike arcs, footwork. He kept the cells off. He kept his tempo internal, the rhythm he heard in his head rather than the rhythm he put into the world — a distinction that mattered more than most people understood, because the difference between a Rhythmist who needed to express their tempo externally to establish it and one who carried it internally at all times was, roughly speaking, the difference between a musician who could only play with sheet music in front of them and one who had internalized the score.
He was aware of Sera behind him, aware in the particular way that two Resonance users in the same space were always aware of each other — not hostile, but alert. Her harmonic frequency was subtle, a low-level ambient resonance that wasn't performing anything, just present. Like the sound a tensioned string makes before it's played. He found himself instinctively setting his warmup rhythm at a frequency that didn't conflict with it, a minor adjustment, unconscious at first and then deliberate.
"You adjusted for me," she said.
He turned. She was watching him with an expression that was more curious than anything else.
"Instinct," he said.
"Most fighters don't bother. Especially Rhythmists." She tilted her head. "You're not formally trained."
"No."
"Where did you learn to accommodate existing resonance?"
Kael hesitated. This was not a question he was accustomed to answering, partly because very few people had ever been calibrated enough to ask it, and partly because the answer — that he had learned it by listening obsessively to the same forty-three-minute recording for eleven years and working out the underlying principles by feel — was the kind of answer that made him sound like a fanatic.
"Practice," he said.
Sera looked at him for a moment. She seemed to file the incomplete answer the same way he had filed the measurement of forty-one centimeters — as a data point to be returned to later.
"Your footwork is unusual," she said. "The strike pattern on your rod work. You're building tempo from movement, not from discharge."
"The discharge is the last thing," Kael said. "The movement establishes the rhythm first."
Something shifted in her expression. Not surprise exactly. More like recognition. "That's Seren's method," she said.
Kael went very still.
"His early interviews," Sera continued, watching him. "Before the last concert. He talked about it in a few of them — the idea that Rhythmist technique builds from the body outward rather than from the cell outward. It's not standard Academy teaching." She paused. "Most people in the Lower Tiers don't have access to those interview archives."
"The one about the body as the first instrument is publicly available," Kael said.
"One of them is. The others are in the Academy archive." She studied him. "You've seen more than one."
He had. He had found them in fragments, on the secondary nets, on hardware-shared data packets that circulated in the Lower Tiers through channels that were technically in violation of the city's intellectual property frameworks. He had spent a year collecting them. He had watched each one until it stopped teaching him anything new, and then watched it again to make sure.
"I got what I could," he said.
Sera nodded slowly. She had the expression of someone revising a prior assessment. "The Academy keeps most of Seren's recorded material in restricted access. Alumni and active students only."
"I know."
She looked at him for a moment longer, then turned back to her own practice. "Your timing on the third beat of your left-hand sequence is slightly ahead," she said. "You're anticipating."
Kael returned to his warmup. He focused on the third beat. She was right — he was anticipating, by maybe ten milliseconds, a micro-advance that was barely perceptible but would compound into a drift problem at higher tempos. He had not noticed it before. He had been practicing alone.
He fixed it, and started again.
They worked in the same space for another twenty minutes without speaking. When Sera's time was up, she gathered her things with the efficiency of someone who had places to be and went to the door. She stopped with her hand on the frame.
"Rennick's facilities are for Rennick's purposes," she said, without turning around. "Don't mistake access to a space for access to what the space can teach you. Those are different things."
She left.
Kael stood in the twenty-meter room with the resonance-treated walls and the calibrated equipment and the absence of the ambient harmonic frequency she'd been generating, which he noticed now only because it was gone.
He thought about what she'd said.
Then he set his rods, established his baseline, and got back to work.