SANAA (Reuters) - By nightfall, thousands of anti-government protesters in a scrappy tent city in Yemen's capital Sanaa catch their breath and begin to cheer musicians clambering onto a rickety stage.
"Let's give a round of applause for the big hit, "Mother of the Martyr, Bride of Blood," their host shouts.
Sometimes jubilant, sometimes mournful, protest songs -- or revolutionary anthems, as their creators call them -- are the pulse of a nine-month-old movement still struggling to end the 33-year rule of Yemeni President Ali Abdullah Saleh.
Streets that earlier swarmed with motorbikes whisking bloodied protesters away for treatment are instead filled with candy vendors and children. The smell of popcorn drifts through crowds of men cross-legged in the street as singers croon on a platform plastered with photos of those killed in protests.
"They stir my love for the revolution, they lift my spirits," said protester Salem Jabbar, 23, sitting transfixed in "Change Square," the 4-km (2.5-mile) stretch in the heart of Sanaa that protesters occupy with their ramshackle tents.
Some songs extol freedom and bravery, others tell tales of young lives cut short by guns and rocket fire in bloody government crackdowns.
In the morning, organizers crank out catchy, upbeat numbers to draw protesters to the streets. Men, young and old, dance and cheer before heading off on marches that have often sparked deadly clashes with pro-Saleh army units.
"Revolutionary anthems keep your feet moving," said Yahya Aziz, a 23-year-old dancing with friends, stomping and waving their arms in the air. "We don't love death, but there's no going back. We must bring down the regime."
The most popular anthem by far, Yahya's friends agree, is "Hurriya" (freedom) by Khaled al-Zaher.
Zaher, a Yemeni university student, plays the song in a friend's living room-turned-studio with the grimace of a jaded rock star tired of fans clamoring for the same old hit.
The chorus, sung to an addictive dance beat, translates as: "Freedom. A free people, rooted deep in the mountains. Freedom. With faith to go down the path of struggle. Freedom."
Zaher said he had called up the beat to order. "You tell the music mixer what rhythm you want: oriental, Bedouin, Western. With 'Hurriya,' I requested a samba beat," he said. "But I'm thinking next time I want to try rap."
Revolutionary anthems, Zaher says, are a collaborative process: singers compose a tune and then coordinate the lyrics with local poets. Then they send the composition to a mixer for special effects and background music.
Zaher, a household name for protesters, is harassed by Saleh loyalists at home. He hides out in his friend Abdullah's studio, where they make do with a lone microphone and computer.
The music business has soaked up their savings. Both are unemployed and they pay for their mixes, and like most protest musicians, they refuse money for their songs.
"There's no financial profit in the revolution. You do it out of personal conviction. It's our jihad (holy struggle). We pass the message of revolution in our songs. This is the least we can do," Zaher said. "I would accept donations though."
The musical messages have evolved with the protest movement. Songs like "Hurriya," with themes of freedom and justice, were popular at first. Later, musicians turned to songs praising those who were killed in demonstrations.
"We talk about what themes we want to focus on next... Right now our songs are about revolutionary victory, to encourage our youths to keep going," said Abdullah, Zaher's singing partner.
Zaher's latest song, "Allahu akbar (God is great)" was inspired by his experience of marching in protests in September, when clashes with the army killed around 100 people.
"The army fired and the people in front of me didn't move," he recalled. "I felt a fervor when I heard them shout, 'Allahu akbar.' You are flushed with emotion, you can't back down."
If you need lyrics, Zaher says, you go to Duhaq al-Dhabyani, a wistful 38-year-old poet, who wanders through Change Square in a worn leather jacket, whiling away the day talking politics or writing songs.
"My relationship with poetry started in childhood. I've been trying to write since I was seven years old," Dhabyani says, sipping tea at a run-down cafe surrounded by protest tents made of plastic tarpaulin.
Dhabyani has written about 40 protest songs for artists across Yemen. He raises his finger and interrupts himself to recite the chorus he wrote for Zaher's latest song.
"Allahu akbar, the revolutionaries are coming, closed ranks for the great day forward. One heart beats, one voice shouts."
Dhabyani, on strike from his post at the education ministry since protests began, says music brought the movement to life.
"I wrote the first revolutionary anthem, they sang it on the first day of protests. I believe music helped set off the revolution. When we first tried to protest, we were still very scared. It is as if the song broke a wall of fear."
At least 500 songs have been made by dozens of artists in Yemen's protest movement. After musicians perform them live at Change Square or in other Yemeni cities, the songs instantly reappear as mobile phone ring tones or as mixes on You Tube.
Dhabyani says recording artists plan to use their music to envision a future after the still-unfulfilled revolution.
"The challenges ahead are much bigger than toppling the regime now," he said. "We must call for tolerance, to forget the past and rebuild the country for a better future."
For many protesters, that may seem difficult to imagine as Saleh clings to power despite stalled political talks, a surge in bloodshed, and the steady creep of crushing poverty.
Dhabyani says it is his duty to be optimistic: "Of course I am hopeful. Once the poets are lost, where will the others be?"
Reporting by Erika Solomon; Editing by Alistair Lyon