“It is song about a camel. The camel is angry. It is asking the owner why he bought a pickup truck.”

“It is a song about a war.”

“It is a song about traveling.”

“It is a song about love. There are so many songs about about love.”

We are sitting in a shack outside of the ruins of Petra, Jordan, listening to Bedouin music.

Petra: the hidden heart of Nabatea—a 2,300-year-old empire, a crossroad of antiquity, of fabulous monuments, of palaces and grand avenues chiseled into a sandstone canyon far above the Rift Valley of Jordan. Towers. Columns. Stairs. Altars. Pediments. Aqueducts. Palaces. Petra is a city scooped from living rock. Its architecture rivals the majesty of Rome, the clean beauty of classical Greece—just two of the many empires with whom it traded. The Nabateans were once nomads, proto-Arabs. For centuries they monopolized the incense trade. Their gods are depicted as cubes, as pure geometry, as triangles, as abstract squares. (Al Qaum, the warrior god, a night deity who protected the caravans, was a guardian of all sleepers, whose wandering souls took the form of stars.) They held wine-soaked feasts for their dead. In Mada’in Salih, Saudi Arabia, they carved gigantic tombs from bergs of rock that stand like colossal Fabergé eggs in the barren deserts. Awesome. Imposing. Monuments to raw power. To monomania.

Qasim Ali sings the blues, Bedouin style, at Petra, ancient heart of the Nabatean empire. Photograph by Paul Salopek

In the tin shack, Qasim Ali tightens the string on his rababa. He plucks it, listening.

The rababa is perhaps the oldest stringed instrument in the world: a Bedouin fiddle. Qasim draws the bow across the single string. He sings a sad song about an old man abandoned by his sons in the desert, a lament of ingratitude, of fecklessness. (You can play Qasim’s song above.) The sky outside is lidded with clouds. A cold rain has fallen. Inside the shack a wood stove ticks with heat. The air is yellowed by a naked bulb, by a nimbus of cigarette smoke. Other men sing along. They are all Bedul, a Bedouin tribe that migrated into the region just 200 years ago, from where nobody knows. Yet their music sounds older than the ruins around us. Nomad chords. Repetitive, sinuous, smoothed and eroded by time like the red Umm Ishrin sandstone from which Petra is carved: Paleozoic rock that flexes like a muscle along the Rift Valley, the crack that stretches southward beyond the rim of the world, all the way back to the beginning, to our journey’s start in Ethiopia.