According to the International Center for Prison Studies, India houses some 330,000 inmates in its prisons
Strutting across the stage wearing red stilettos, red lipstick and a flower in her hat, Samara Chopra was always going to be a hit with the inmates of Tihar high-security jail in New Delhi.
The audience of about 1,000 male prisoners whooped with delight as Chopra, lead singer of the Ska Vengers, ran through a high-energy one-hour set at an afternoon concert inside the prison grounds.
Clapping her hands high in the air, and belting out ska, reggae and soul classics, she soon had the prison guards as well as the captive audience moving to the music.
The event was an unusual break from the daily routine at Tihar jail, a vast complex in the west of the Indian capital where 12,000 inmates ranging from trial suspects to convicted murderers are incarcerated.
"Music is a force for good," Chopra, 28, told AFP during a warm-up act by prison band The Flying Souls.
"It has the power to change people and is fundamental to all lives, including those inside prisons," she said. "The interaction we have had with the people here has been great and I want to come back and teach here."
The Ska Vengers, a popular Delhi band, have developed links with "Jail 4" at Tihar, and they held the gig to celebrate arranging for 300,000 rupees ($5,700) of music equipment to be donated to the prison by a music store.
"Jail 4", one of 10 separate facilities within the prison, houses 1,615 inmates including 160 foreigners and 230 convicts, four of whom are on death row, according to an official register at the entrance gate.
One of the convicted murderers, Ashish Nandwana, 26, from Jaipur, was among the raucous concert crowd gathered in the prison gardens.
He is serving a life sentence for stabbing a trainee flight attendant to death in a Delhi guesthouse in April 2008 after she refused to marry him.
"It is good to have music here. The prison is ok but we want to have events like this," he told AFP before the concert.
Such grim personal stories seem at odds with the cheerful atmosphere at the concert, which was attended by guest of honour Neeraj Kumar, the director general of Delhi prisons and a keen advocate of music for inmates.
"We have been introducing music rooms and we are very happy to say that the response has been tremendous," he said. "It is therapeutic.
"Prisoners vent and give release to creative energies, and we are trying to reform them through music," he said, adding that one female inmate had been suicidal until she had access to music instruments.
"We have done this for one year now, including for Bengali music, Hindi classical and Western classical, but (Bollywood) film music is the most popular."
Kumar said he was "pleasantly surprised" by the depth of talent among prisoners and that he had recently started a "Tihar Idol" competition to select inmates who will make a commercially produced album.
The idea of providing Tihar with better music facilities came from Stefan Kaye, the London-born keyboard player of the Ska Vengers who found very little equipment on offer when he held music workshops in the jail late last year.
"Working with inmates is no different to working with anyone else," he said. "They do usually want to tell me what crimes or charges they are in jail for, but I have never felt at all threatened."
"In fact, they are just very keen to learn, desperate for anything to distract them from the monotony and negative thoughts of jail life. They take music very seriously and often display extraordinary abilities."
Among the kit donated to Tihar were drum sets, tabla Indian drums, keyboards, amplifiers and crucial smaller items such as scores of guitar strings.
"It helps so much, and perhaps the skills will be useful when they leave the prison," said Kaye. "When I spoke to (Delhi music shop) Furtados, they gave us everything we asked for free."
Tihar jail has a record of innovative rehabilitation schemes for prisoners including yoga, meditation, art classes and a shop selling products made by inmates.
Guards even allowed a handful of the jail's best dancers to squeeze out of the crowd to show off their wildest moves in front of the stage, triggering the biggest cheers of the day from their delighted comrades.
Support act The Flying Souls, a band formed in Tihar last year by three convicts and seven remand prisoners, struck a more poignant chord with their songs about loss, longing and the pain of separation.
"We're all stressed. We're all away from our homes and we miss our families. There are problems with our cases, they get so delayed," said lead singer Amit Saxena, 35, who has spent nine years in jail as his murder trial drags on.
"It's only when we're in the music room that we don't remember or think about all these things," he said. "Everyone really loves their wife or their family. Some people's girlfriends are still waiting for them on the outside.
"We remember them, that's why we write more romantic songs."