There's this instrument called the "a'reng", played by the Pako people in Vietnam and Laos. It's one of the craziest most beautiful most perplexing musical instruments on Earth. We set off for Vietnam to try and see if we could find it. We ended up in a lush mountain valley with a single hut, home to an elderly couple who are the keepers of the Pako musical tradition. Together, they dashed our hopes and expectations in the most wonderful way.