She hung back to let everybody else go ahead of her, then tramped up a well-worn path through a field of higher-than-head-high boulders, all smooth and round. Stepping stones took her across an icy patch of marsh to a sort of absurdly steep stairway built into a twenty-metre cliff of naked rock. It was so steep it was nearly a ladder. She used the ropes on either side and climbed, following a lumbering local with a giant woven basket on its back; it heaved itself up, corner feet fitting into the creased steps, its elongated prehensile side-corners curling round the thick ropes like hands. It achieved the cliff crest with obvious effort, hauling itself over a low wall.

Tefwe followed, clambering further up and then over into the wave-wash of vast, bone-battering sound. She felt her ears closing up, reducing the immediate impact of the colossal noise, but she could still feel it through her head, through her teeth.

She stood in the side-on evening light, looking slightly downhill to the hearkenry.

The Ahen’tayawa hearkenry on the slopes of Mount Jamanathrus was a collection of modest, low buildings scattered across the stony ground to the rear of the open-fronted cells that formed a long curve facing the mountain itself, which rose – steep, sheet-smooth – from the high plain ahead, its summit obscured by broad rivers of orange-white cloud.

The sky-filling, soul-battering, ear-splitting sound came from the Timbrelith Caverns: tens of thousands of enormous tunnels bored into and through the tops and flanks of this part of the Querechui Mountains millennia ago by long-departed aliens many centuries before the Uwanui had colonised this part of their world. As was so often the case with enigmatic alien artefacts, the general assumption was that the work must constitute Art.

The Sound was the result of Cethyd’s prevailing Belt Winds coming thundering through and across those colossal pipes, creating a noise like an orchestra of hundreds of gigantic organs all playing a changing selection of most of their available notes at the same time, with all their stops pulled out. It varied according to the strength and direction of the various winds, how the gusts curled and twisted around the peaks, and whether the local jet-stream was scouring across the peaks of the mountains as well; when that happened – fortunately only every few years – the Sound could reach pitches and strengths that could deafen people kilometres away and bring down buildings in the surrounding hearkenries.