Maria Teresa Schuster changes into a shiny, silver pair of high-heeled shoes and readies herself to climb onto the stage.
These shoes are a veritable "license to fly," she says.
There are many elements to a good tango: posture, balance, the male lead; but for many elite women dancers, it is the shoes that matter most.
"The tango shoe is something very special. It has to shine, have a beautiful heel, make me feel stronger, more powerful," said Schuster, 72, a regular at the Parakultural Milonga (local tango hall) in Buenos Aires, where the world championships are currently taking place. The competition runs from September 6-18.
A cardiologist and pianist, Schuster has been dancing tango for 20 years.
"When I put on the shoes, I feel like someone does when they put on gloves suggestively to prepare themselves for something intense," she said.
"The shoes are like a license to fly on earth. They have to mold to the foot, and one feels that they caress and are caressed at the same time."
- Groundbreaking designs -
For Carla Marano, an internationally renowned professional dancer, "the shape of the leg becomes aesthetically different -- better in my view -- when you dance in heels.
"And it's functional: dancing in high heels makes it easier to shift your balance forwards, onto the metatarsal and the toes, which is essential in the tango."
During the pandemic, music therapist and tango teacher Marina Kenny asked a dozen great dancers to describe their relationship with their shoes for an e-book.
One of the dancers, Mariela Sametband, wrote: "The shoes are to tango what a guitar is to a guitarist, a broom to a street sweeper or a knife to a chef."
"It's the instrument through which we express ourselves. Of course it is our bodies that move... but the shoes are an essential vector, because they connect us to the ground."
A specialist shop in the chic Recoleta neighborhood of Buenos Aires sells the iconic "Comme il faut" brand, mostly to foreign customers.
The store was opened around 20 years ago by two fellow dancers capitalizing on a tango renaissance, after the dance had lost popularity following its golden age from 1940-1955.
"I danced the tango but didn't like the shoes on the market, they were always black and old-fashioned," co-founder Alicia Muniz told AFP.
"I decided to make my own shoes. I took two years perfecting the fit, the height, the comfort and then I took them to the milonga and they attracted attention."
She started "incorporating lace, leopard print, materials that had never been used before," and alongside Raquel Coltrinari created the brand.
- 'A niche, a business' -
Appearances are, of course, important.
"When you dance, people look at your feet. (The shoes) are an attractive object," said Muniz.
More than just aesthetics, the shoes serve a functional purpose, and their design must reflect that.
An almost indestructible steel wire is inserted into the soles, up to the toes -- which cannot be pointy -- while the shoe is fastened with a strong strap.
All these elements are essential for acrobatic tango moves.
"The soul of the shoe is the arch," which must be carefully chosen to perfectly fit the arch of the foot, Muniz explained.
As for the heel, "the highest are 9.5 to 10 centimeters (3.5 to four inches). Anything more and you would not be able to dance without twisting your ankle," said Muniz, who also makes shoes for men with a slight lift in the heel.
According to tango instructor Moira Castellano, "the heels can be your greatest ally or your worst enemy."
"Comme il faut" -- a name borrowed from the title of a 1917 tango performance about a lost Parisian love -- sells around 15,000 pairs a year, exporting to Europe, Japan and the United States.
It also supplies professional dancers in Buenos Aires.
Tango accessories have become "a niche, a business," says Kenny, who wrote the book on tango shoes.
The industry is a far cry from the impoverished migrants to Buenos Aires in the late 19th century, who supposedly invented the tango and performed it in their regular shoes.
No matter how important the shoes are, though, they should never prevent "the immense pleasure" that dancing gives, says dancer Analia Vega.