EYDER PERALTA, HOST:
Mexico City is chaos.
UNIDENTIFIED PERSON #1: (Speaking Spanish).
PERALTA: Twenty-two million people live here, and everywhere you turn, someone is trying to get your attention - the bread guy, the trash collector...
(SOUNDBITE OF BELL RINGING)
PERALTA: ...The guy who sells water...
UNIDENTIFIED PERSON #2: (Speaking Spanish).
PERALTA: ...Or the one who sells tamales from Oaxaca.
UNIDENTIFIED PERSON #3: (Speaking Spanish).
PERALTA: But there is no sound more iconic, more recognizable than this.
MARIA DEL MAR MARTINEZ: (Speaking Spanish).
PERALTA: Trucks drive around every corner of the city bidding to buy your old stuff - mattresses, refrigerators, or any old piece of iron that they can recycle.
MARTINEZ: (Speaking Spanish).
PERALTA: It's like the street equivalent of a nagging infomercial. The sound is so ubiquitous that the first words of Spanish that popped out of my 3-year-old's mouth were...
UNIDENTIFIED CHILD: (Speaking Spanish).
PERALTA: I tracked down Maria del Mar Martinez at her house in the outskirts of Mexico City.
MARTINEZ: (Speaking Spanish).
PERALTA: On the walls of the living room, she has a piece of art that that honors her trajectory. When she was 8 years old, she worked as a clown at kids' parties. And then 19 years ago, when she was just 9 years old, she and her dad recorded (speaking Spanish).
MARTINEZ: (Through interpreter) On this wall, I want to put the cassette because when we first recorded, it was on a cassette.
PERALTA: At the time, her dad was pushing a cart around Mexico City, and he would call out for potential customers using a cardboard megaphone.
MARCO ANTONIO AGUILAR: (Speaking Spanish).
PERALTA: Marco Antonio Aguilar is a sentimental guy. The memories fill his eyes with tears. Those were hard days, he says. He remembers having to work right after surgery. He remembers how the weight of the cart stretched his stitches. His daughter puts her hand on his shoulder.
MARTINEZ: (Speaking Spanish).
PERALTA: Marco Antonio is a single dad, and they've always been together. Ever since they can remember, she's been walking alongside him, buying old stuff in Mexico City.
AGUILAR: (Through interpreter) I bought her goggles and gloves, and when she got tired, she would just ride on the cart.
PERALTA: To make work a little easier, one night they stayed up late until all the other sounds in the city went quiet, and they recorded (speaking Spanish). When they took it out to the streets, their business took off, and everyone asked, where did you get this? They would ask...
AGUILAR: (Through interpreter) How much would you sell it for? I'd just say, just give me five pesos for the cassette.
PERALTA: Like a hot mixtape in Houston, the cassette made its way across the city, and within a year it was everywhere. The recording was being used by dozens - who knows? - maybe hundreds of upcyclers across Mexico City. Maria del Mar says what gave her pleasure is that it became the soundtrack of a kind of work that she calls magical. Some old lady sells you an old TV - a young woman, a beat-up washer.
MARTINEZ: (Through interpreter) And then you have to remove this part or strip that cable, and you think, whoa, I am feeding my family like this.
PERALTA: Sometimes they would leave with 30 bucks, a teeny bit of gas and come back home with 1,700. Marco Antonio says he remembers one day when they hardly had any food at home. He had spent all day roaming the streets and had bought nothing. In nearly every neighborhood in Mexico City, there are these little shrines to the Virgin of Guadalupe. Marco Antonio says he stopped his truck and prayed at one of them.
(SOUNDBITE OF ENGINE STARTING)
AGUILAR: (Through interpreter) I restart the truck and people start coming out - something magical. And people began taking out their old things like a miracle.
PERALTA: In the 19 years since, their recording has appeared in movies, on TV - musicians have taken inspiration.
(SOUNDBITE OF SONG, "SE COMPRAN")
MEXICAN INSTITUTE OF SOUND: (Singing in Spanish).
PERALTA: Maria de Mar and her dad have recorded ads for other companies. They've made enough money to buy themselves a newer, more efficient vehicle to keep doing what they love. And as always, father and daughter hop on...
(SOUNDBITE OF ENGINE STARTING)
PERALTA: ...And they do what they've always done.
MARTINEZ: (Speaking Spanish).
PERALTA: But now she screams her iconic pitch live because that's what people want.
(SOUNDBITE OF MEXICAN INSTITUTE OF SOUND SONG, "SE COMPRAN") Transcript provided by NPR, Copyright NPR.