When they were played, he said, "the music expelled the demons they held, as well as being a requiem for lives lost."
For the project titled "Disarm," Reyes said he was able to choose his instruments from about 6,700 guns that were turned in or seized by the army and police in Ciudad Juarez, a city of about 1.3 million people that averaged about 10 killings a day at the height of the violence. In 2010, Ciudad Juarez, across from El Paso, Texas. Juarez had a murder rate about 230 per 100,000 inhabitants. The nationwide rate for the U.S. that year was 4.8.
"The dramatic thing is that this is just the tip of the iceberg of all the weapons that are seized every day and that the army has to destroy," Reyes said in an interview as he demonstrated some of his computer-controlled instruments that played a sort of industrial pop tinged with marimba.
Reyes already was known for a 2008 project called "Palas por Pistolas," or "Pistols to Shovels," in which he melted down 1,527 weapons to make the same number of shovels to plant the same number of trees.
The new project began last year with a phone call offering him another chance to work with the seized guns.
"Normally, they bury or destroy them, but someone who works in the government said, 'Would you be interested in making a sculpture with this metal?' " he recalled.
Drug-cartel violence cost more than 70,000 lives in Mexico over the past six years and the weapons trafficking has been a sore point; many of the weapons used by the cartels are smuggled across the border from the United States.
In 2012, then-president Felipe Calderón inaugurated a billboard in Ciudad Juarez that, facing Texas, spelled out the words "No More Weapons" in welded pieces of decommissioned guns.
Reyes also hopes to take his message international, with an exhibition of the musical instruments in London's Lisson Gallery in March and later in the United States.
"This project has a pacifist intent, to create a global consciousness about arms trafficking," Reyes said.
Violence has become a theme in Mexican art in recent years. One artist from the violence-plagued state of Sinaloa, Teresa Margolles, works with artifacts collected from crime scenes, such as pieces of glass or cloth dabbed with mud and blood.
Reyes stresses that his work "is not just a protest, but a proposal."
"It occurred to me to make musical instruments, because music is the opposite of weapons," he said. "This exercise of transformation we see with the guns is what we would like to see in society."