Just a few months ago, Ali Naema was playing in the Syrian army band.

Today, he's making war, not music -- but with the rebels, having swapped sides and his trumpet for an AK-47 assault rifle to join the fight against his former comrades with the aim of toppling President Bashar al-Assad.

"I was in the military band for two years," Naema, 24, tells AFP in Aleppo, where he is now part of a katiba (rebel unit) fighting to wrest the city from the regime.

Conditions in the army were tough, he says. His commander stole 70 percent of his $100-a-month salary. And when he got sick he had to pay for his own hospital care.

As the civil war worsened, he saw fellow soldiers loot, rape and steal from Sunni civilians.

Defection was his only solution, the bearded young man -- himself a Sunni Muslim -- says in a soft voice.

He looked for a chance to defect for six months while stationed in a rural area, but the threat of being killed by watchful commanders was too great.

It was only when he made contact with a rebel fighter in Aleppo, Ahmed Jamel, via Skype that he saw how to do it. In September, he paid $50 to an officer for family leave, caught a flight to Aleppo and changed into civilian clothes.

"As I left the base, Ahmed and some FSA (rebel Free Syrian Army) people came in a car and picked me up," Naema says.

"I was very scared. I didn't know what would happen. I was afraid maybe they were terrorists and they would kill me.

"But they kissed me on both cheeks and congratulated me. And I felt safe, and very happy."

Like many of the conscripted troops who have joined the rebels, he decided to stay to fight the regime, rather than make his way to refugee camps around the Turkish border where conditions are rudimentary at best.

He was given cursory weapons training -- something he never received in the army, he says -- and now totes his knock-off AK-47 with the same nonchalant pride as other rebels in Aleppo, his musician's fingers curled around its forestock.

A trickle of defecting troops is slowly swelling the rebel ranks. Insurgent commanders believe many more want to join them but are prevented from doing so.

The rebels give varying estimates as to the number of defectors who arrive each day, ranging from a dozen to four times that.

One commander, Abu al-Moatissim, 39, fills out and signs printed slips of paper bearing his brigade's logo on it by candle light inside a building.

His right hand gripping the pen is fingerless, scarred from a home-made mortar round that went off as he was loading it.

The paper is carried by the turncoat newcomers to establish them as bona fide rebels, and gives them the right to food, lodgings "and cigarettes, if they smoke," Moatissim says.

"We don't give them any money. And it doesn't matter if some of them are sent as spies or anything, because they never get to meet the commanders who decide things, or see anything strategic."

Two-thirds of the regular army conscripts switching sides stay to fight, "and in some cases die" with the FSA, he says.

Most defecting Syrian military officers, though, head north to Turkey, where they are housed in a separate camp that is off-limits to other Syrians and to media, he admits.

"The honourable ones stay to fight," Moatissim says, adding that several of those who did have more than proved their value. "Without them, we wouldn't have been able to take many of the important bases and positions we have."

For Naema and other conscripts like him who have chosen the rebel side, taking orders from former army officers in the struggle against the regime is meaningful.

"I joined to battle the injustice" seen in Syria's army, both within and in its treatment of civilians, Naema says.

But the musician-turned-guerrilla still hopes that one day he will be able to drop his rifle and go back to what he loves.

"When it's all over, I want to go back to music. Maybe start my own band."