The 10 tracks showcased Ms Devine's prodigious singing and songwriting talents but also served as a personal memoir and window into her battle with mental illness.

"Those sessions with her were some of the best work I've ever done in the studio," McLaren said.

"Music was her therapy for what happened in her past."

He awoke on Wednesday morning to the news that human remains found in a Blue Mountains dam in March belonged to his friend who had been missing for almost eight months.

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"It's so sad; she was such a beautiful, unique talent and character," McLaren said.

"I feel we got pretty close when we were working together. There were some pretty heavy moments but mostly we didn't stop laughing."

Social media was flooded on Wednesday with an outpouring of grief for the 41-year-old Waratah resident who had been reported missing from her Turton Road address on September 5, 2018.

"Such sad news and a devastating outcome for her and her family. She was a very dear friend of my daughter and our family," one friend wrote on Facebook.

"I hope they catch who is responsible for this cruel act may you be resting in peace sweetheart my thoughts and prayers are with her family xx."

Police released a public appeal for help to locate Ms Devine on December 21 last year - the date of her 42 birthday.

The appeal said family and friends called police when they couldn't find her and it was believed she might have travelled to Sydney.

There were reported sightings of her in the Hornsby and Blue Mountains areas shortly after she was last seen.

Sydney Water Catchment Authority employees discovered Ms Devine's skeletal remains in remote bushland at North Katoomba on March 18 this year.

"It had been there a fair while," Detective Inspector Scott McAlpine said on Wednesday.

"It's a closed-off area, it's not open to the public because it's a catchment area for the Sydney water authority. Tourists wouldn't probably go there as a matter of course."

Police have searched the dense bushland and dam several times for clues without success.

While the cause of her death has still not been determined, Inspector McAlpine said police believe Ms Devine was murdered.

Strike Force Eking, comprising local police and homicide squad detectives, was launched to investigate Ms Devine's disappearance and murder.

Police are presently attempting to piece together her last movements.

Inspector McAlpine said Ms Devine had shopped at the Rivers store in Katoomba and Coles supermarket on September 6, 2018.

"One of the last known sightings of Cecilia Devine was her leaving this hotel and walking down one of the main streets of Katoomba," he said.

CCTV footage also captured her buying some food, a scarf, a jumper and shoes from shops in Katoomba.

But nothing was found with her body or nearby.

Her brothers Nathan and Troy Pearson made an impassioned plea on Wednesday for information about their sister's disappearance.

Nathan Pearson said his sister, who was also known as Kristen Pearson, loved making music and was "probably way too easygoing".

"She just loved being part of the social life, that's where she was devoted with her singing," he said.

"She'd assimilate with anyone."

Troy Pearson described his sister as "very much family based."

"We wouldn't see a harmful bone in her body," he said.

Ms Devine spoke about her 'run in with mental illness' in New York in 2013 during an interview in the lead up to her album launch.

"I was psychotic through three or four episodes while I was over there on my own," she said.

"It was very serious. Thankfully I had a good network of people to get me back safely.

"I made a promise to myself to remember everything that happened to myself. I would try to write an album that basically told my story, to give me permission to feel the feelings that I felt and the brutality that I experienced."

Mr Pearson confirmed his sister had suffered from bipolar disorder.

"That plays a big part in her issue," he said.

Detective Inspector McAlpine urged anyone with information about Ms Devine to speak with police.

"We believe there are people out there who spoke with Cecilia or saw her at the time and we urge them to come forward," he said.

"We're all wanting the same outcome - to find answers for Cecilia's loved ones. They need to know what happened to her and how she came to be where she was."

Anyone with information should contact Crime Stoppers on 1800 333 000 or https://nsw.crimestoppers.com.au.

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