Tomb of Marquis Yi of Zeng

Stand still for a moment and listen. The sounds here are small: shoes on stone, a low voice somewhere behind you, the hum of a quiet hall. It is hard to believe that this patch of ground in Suizhou once held one of the loudest instruments of the ancient world. For about two and a half thousand years, that music lay silent under red earth and dark water. Then, in the late 1970s, it came back.

The story of its return begins by chance. In 1977, soldiers were levelling a low hill on the edge of the city, a place known as Leigudun, to make room for new buildings. Their work exposed soil of a different colour, a sign that people had dug here long ago. Archaeologists came to look. In 1978 they began a full excavation, and they soon understood that they had found something extraordinary.

The tomb belonged to a ruler called Yi, a marquis of the state of Zeng. That title meant he was a regional lord, not a king, under the old Zhou order of ancient China. He lived during the early Warring States period, a time of rival states, constant war and great invention. Inscriptions found with him point to a death around the year 433 before the Common Era. That date puts him in the same broad century as Socrates in Greece.

Now picture the burial itself. Workers did not build this tomb on the surface. They cut it down into the rock of the hill, then lined the pit with huge timber beams. The result was a set of four wooden chambers, arranged in an irregular shape rather than a neat rectangle. Each chamber had its own purpose. One held the marquis. One held his music. One held weapons and chariot fittings. Another held people who went with him into death.

That last detail is the hardest part of the story. Inside the tomb, excavators found the coffins of about twenty young women. Most scholars believe they were musicians, dancers or attendants, and that they were sacrificed to serve their lord in the afterlife. Visitors often move quickly past this fact. It is worth a pause. The beauty in this tomb came with a human cost that the people of its time accepted, and we do not.

Here is the first surprise. When the excavators opened the burial, the chambers were full of water. Groundwater had seeped in over the centuries. You might expect water to destroy everything. In fact, it helped. The cold, wet, low-oxygen conditions slowed decay. Wood, lacquer and silk-wrapped objects survived far better than in many dry tombs. There was also evidence of an old robbers' tunnel, but the great treasures were still in place.

The central chamber held the reason the world knows this name. It is a set of sixty-five bronze bells, called a bianzhong, hung on a large wooden frame in three tiers. Bronze figures in the shape of standing warriors hold up the beams. When archaeologists found it, the frame was still standing in the water. The bells hung where the marquis's musicians had left them.

And here is the second surprise, the one most visitors miss. Each bell can play two different notes. Strike it in the centre and you hear one pitch. Strike it near the edge and you hear another. This works because the bells are not round. They have an almond-shaped cross-section, like two curved tiles pressed together. Bronze casters in this period understood sound so well that they shaped metal to hold two voices at once.

The bells also carry writing. Thousands of inscribed characters run across their surfaces. Many of these words describe musical pitches and how the tuning systems of different states matched each other. In other words, the bells are both an instrument and a textbook. They show that musicians here worked with a full twelve-pitch system, centuries before most of the world wrote down anything similar.

The marquis's own resting place deserves attention too. His inner coffin is wooden, covered in red and black lacquer, and painted with guardian figures and twisting creatures. On its sides, painters added small doors and windows. Many scholars read these as openings for the soul, so that the spirit could move freely. Other objects from the tomb include a lacquer box with an early painted record of the stars, showing the Big Dipper among a ring of constellations.

You should know one practical thing as you explore. Most of the famous originals, including the bell set, now live in the Hubei Provincial Museum in Wuhan, the provincial capital. At the site here in Suizhou, the experience centres on the place itself: the shape of the burial pit, the scale of the timber chambers, and the displays that explain what came out of the ground. Standing here gives you something a museum case cannot, which is the setting.

It also helps to know who the people of Zeng were. For a long time, old texts barely mentioned them. Historians debated whether Zeng was the same as Sui, a state named in ancient records, and that question gave this city its name. In recent decades, other Zeng cemeteries have been found around Suizhou. Step by step, a forgotten state is coming back into view. Locals also link this region to Yandi, a legendary ancestor of the Chinese people, but that tradition is legend rather than history.

Before you leave, look once more at the ground beneath this place. Under these hills, a lord was laid down with his bells, his weapons, his star map and the people he could not live without. Water kept them all for twenty-five centuries. As you walk back out into the streets of Suizhou, listen to the traffic and the voices around you, and remember that this quiet hill once held a full orchestra, waiting in the dark for someone to strike the first note.