Irbil, Iraq (CNN) Not far from Mohamad Al Mawsily's studio, fierce battles are raging to oust ISIS from the northern city of Mosul. But from his secret location, the young Iraqi businessman is waging another war against the militants on a daily basis. Less bloody? Yes. But, still potentially lethal.

There are no bullets and bombs in this building. No high-definition images of war being broadcast to the world on TV or social media. Here, there are only two things that ISIS hates: music and truth.

Almost a year after ISIS imposed its signature tyranny in Mosul and surrounding Nineveh province, Al Mawsily and two partners launched a radio station for the million or so residents left trapped in the beleaguered city. They named it Alghad, or tomorrow, in hope of a better future

Alghad FM broadcasts into Mosul as well as online, where displaced Iraqis around the world can listen.

Alghad FM defies ISIS with its programs, and so everything about the station has to be kept underground, including the identities of the staff. Al Mawsily means "from Mosul" and is not the 28-year-old founder's real name. He didn't even tell his own parents about his clandestine endeavor, though they eventually pieced it together.

Alghad's studio in the relatively safe Kurdish region of Iraq -- CNN was invited there after a pledge to not give away the location -- offers no signage or other visible clues the station is relaying the voices of Mosul that would otherwise go unheard.

"It was a way for us to break the siege by Daesh," Al Mawsily tells me in his office on this evening, using the Arabic term for ISIS.

We have loyal listeners in an abnormal time and in an abnormal situation. Al Mawsily

I've arrived just in time for the start of Alghad's popular 50-minute segment called "Deliver Your Voice." The talk show is similar to others in many ways, except one: Most of the callers are from a city under siege.

"We have loyal listeners in an abnormal time and in an abnormal situation," Al Mawsily says. "It is important to break the ideas of Daesh. They want people not to trust each other."

Those listeners include people from Nineveh province displaced from their homes by violence. They live elsewhere in Iraq or as refugees in Europe, Australia and the United States and live-stream the broadcasts online.

"We've developed a Moslawi community," Al Mawsily says. "The radio station is their way of communicating with their loved ones."

ISIS plunged Mosul, Iraq's second-largest city and once its most diverse, into darkness, severing it from the outside world. No more satellite television, internet, music, movies, books or anything that contradicted the official militant line. Most recently, ISIS banned cell phones, although some Moslawis still use theirs surrepitiously.

Hundreds of thousands of people, including Al Mawsily, fled ISIS rule and extreme punishment for violating the harshest interpretation of Sharia.

Educated as a computer scientist at the University of Colorado in Denver, Al Mawsily dresses in blue jeans and collared shirts and speaks almost flawless English. He tells me he remembers every detail about the June day in 2014 when ISIS fighters rolled into Mosul, waving Kalashnikovs and black flags.

It was 2 in the morning, long past curfew, when he fled his house with his parents, not knowing he might never see home again. Since then, he's learned that an ISIS commander is now living in their house.

Al Mawsily tossed a few clothes and important documents, including his passport, into a Samsonite carry-on and raced to the Kurdish border with his parents. Normally, the drive takes less than an hour but on that day, Al Mawsily's family was part of an exodus and the journey to the Kurdish checkpoint took nearly 24 hours. His mother and father were so exhausted that at one point Al Mawsily tried to return to Mosul but quickly realized the foolishness of that decision. By the time they hurtled back to Kurdish territory, the white paint of his new Kia Optima had turned ruddy and the body was punctured with dents and scratches from the helter-skelter off-road driving.

The station's hosts don't use their real names on air for fear of retaliation by ISIS.

Still, Al Mawsily knew he was lucky. His family had money and they could afford to establish a semblance of a new life in a new place. So many of his fellow Moslawis were either left to suffer at home or forced into squalid camps housing hundreds and thousands of the displaced.

Although he escaped, Al Mawsily felt compelled to do something that would keep Mosul alive to the outside world. The way to do that, he figured, was to make sure the city's residents were able to break through the censorship and propaganda of ISIS and make their reality known.

He collected private donations and also spent a good chunk of his own money to put the radio station together, complete with sophisticated equipment and a clean décor that includes tufted white leather chairs.

Alghad began broadcasting music, songs and analysis that questioned the credibility of radical Islam and the authority of the caliphate ISIS had declared. It aired the observations and opinions of Moslawis that cast doubts over the ISIS version of life in the city.

Mosul residents have to call in surrepitiously into the radio station since cell phones and the internet were banned by ISIS.

One little radio station had become a prickly thorn in the side of the militants. Its programs burned in the ears of irritated ISIS leaders who began jamming Alghad's signals.

But that only prompted Al Mawsily to invest even more money into Alghad. He bought four powerful transmitters that allowed him to conduct serious battle on the airwaves. These days, Alghad broadcasts over two of its frequencies; ISIS has jammed another; and the last is used to block the Islamic State's transmissions of propaganda.

The clock's hour hand reaches 6. It's time for a two-minute newscast about the day's events.

Iraqi troops and Kurdish Peshmerga liberated some of the mostly Christian villages and towns on the Nineveh plains outside Mosul. "Long live Iraq. Long live Mosul," the reader announces.

Then Ahmad Salim takes the chair to begin the call-in show, which had been airing five days a week but is being extended to seven as the Mosul offensive heats up. Though Ahmad Salim is just his on-air name, his radio voice is authentic: deep, smooth and soothing.

His first guest is Rahma, a young woman from Mosul who describes artillery and mortar fire throughout the day, especially on the west bank of the Tigris River. Subsequent callers confirm Rahma's account and say people fear the worst.

Men fighting with the Golden Brigades of the Iraqi forces call in to report the liberation of the Christian town of Bartella. In the background we hear singing and celebration, perhaps premature.

"We are ready to sacrifice our blood for Mosul," they chant, blending politics and poetry as Iraqis have done for decades.

Every caller from Mosul takes a risk to call in... Death. Al Mawsily

One by one, callers give accounts of life in Mosul, which Al Mawsily often tries to verify through his contacts in the city.

The callers fear they will be trapped within concrete walls ISIS is erecting in neighborhoods. They describe ISIS booby-trapping buildings and planting IEDs. They say ISIS is lowering its numbers on the streets -- perhaps to fool advancing forces into thinking there won't be much of a fight.

And they talk of their hope of being free.

Toward the end of the show, a woman named Zahra is on air. Salim, the baritone host, asks her about what she is seeing around her. She is audibly upset.

"There is no food. Life is hard. We are in a chaotic situation," she says. "But we don't care if we starve. We just want liberation to come."

Callers from Mosul risk their lives to make their voices heard on Alghad, which means "better tomorrow."

Salim has been composed through the entire show but is now fighting tears. The producers in the sound booth look at each other, not knowing what to do. Salim manages to hold it together. There is defiance, after all, amid Zahra's sorrow.

Al Mawsily is also on the verge of crying. Zahra is the spirit of Mosul, he says.

He tells callers not to identify themselves or give away their locations or divulge specifics about their situations. He is all too aware of the consequences.

"Every caller from Mosul takes a risk to call in," Al Mawsily says. "Death."

He has received threats himself from ISIS, but the danger is so much greater for people still living in Mosul. He feels honored they are willing to take such a huge chance to make the call to Alghad.

"When I sleep at night, I feel like I have done something," he says. "Nothing is as valuable as a drop of human blood."

When I sleep at night, I feel like I have done something. Al Mawsily

Two months ago, a poor man from Mosul called in to the show and said he spent his last few dinars buying cellular call time. It was not to report an emergency or speak with a faraway loved one; the man simply wanted to express himself freely the only way he could: on Al Mawsily's radio station.

The man wanted the world to know he was a proud Mosul resident who opposed the brutal reign of ISIS over his hometown. He called in just to encourage the underground radio station to keep broadcasting, despite the many dangers.

The man said he had no money left after the call and knew that because he had crossed ISIS, he risked death if discovered, Al Mawsily tells me.

"It's not logical in that situation to spend your last dollar on a phone call," he says. "To that man, it was very important. Expressing himself was part of proving his identity."

Al Mawsily carries that call with him always. It buoys him in his unusual undertaking.

He hopes one day soon the radio station will no longer have to operate clandestinely and will contribute to the stabilization process. If and when Mosul is free.