Up a steep road to the top of a ridge, all the mundane falls away.

From here, between the surrounding hills of the Northern Rivers region of NSW, the great heft of Wollumbin Mt Warning is revealed – its forested flanks a blue haze, its rock face summit glistening in the sun. Wedge-tailed eagles ride the thermals above, and rainforest redolent with wildlife runs in every direction.

It is to this place, Uki in the Tweed shire, that Matt Ottley retreated more than 10 years ago. The musician, artist and children’s book author lives surrounded by a raucous avian chorus. In this house – his refuge – he has found peace from the pain of his past.

Ottley has always had a heightened sensitivity to the hurt and beauty of the world. It’s something he shares with the young protagonist in his latest release, The Tree of Ecstasy and Unbearable Sadness. It’s a monumental project comprising not just the book but an accompanying symphonic score on CD, which was performed by a Czech orchestra, and a 50-minute animation created from the book’s 74 paintings and illustrations which is screening in small theatres around the country.

The story follows a boy who, like Ottley, sees things differently. “His gift showed him things so beautiful they made him cry. But it also tormented him with the pain of others that made him feel numb,” it reads. The narrative unfolds around the metaphor of a tree growing inside him: its flower is ecstasy, its fruit is sadness. It was inspired by Ottley’s bipolar disorder, which he was diagnosed with in his 40s.

“The tree really came out of one of my own psychotic experiences where I thought I had something growing inside me,” he says. “It was a plant that was sort of floral in nature. That’s what I wanted to express.”

In the book, the tree morphs into a flying cow, a reptile, then a blue bird, which flies across mountains and oceans into a world of “beauty and wonder”. All of the stages of the journey represent the stages of psychosis – such as in an ancient city, when it encounters an egocentric sovereign with the huge bulbous body of an insect.

“She is the sort of infantile self at the heart of psychosis,” Ottley says. “When you are in that state the other doesn’t exist. The world has become so warped and you’re trying to navigate your way in it.”

Flying over valleys and hills, the boy travels through the stages of fragility and revelation into darkness and tempest – until he comes back into the world and himself with “quietude” and hope.

As we sit on his terrace overlooking the natural vista, freshly baked muffins are placed on the table by Ottley’s partner, Tina Wilson. Ottley is a gentle man, delicate and kind of beatific with long white hair. One of the country’s most popular author-illustrators, he has worked on more than 40 titles – among them last year’s prime minister’s literary award-winning kids book How To Make A Bird, written by Meg McKinlay.

But he says the scope of his creativity has come at a terrible price. It wasn’t until his mid-40s that Ottley was properly diagnosed and treated for type 1 bipolar disorder. By then, he had suffered countless frightening periods of mania and depression, psychotic episodes that would end in psyche wards, and two suicide attempts.

“I have had some very high level creative abilities that are a result of being bipolar – but it is a huge price to pay for that,” Ottley said. “If you could have access to a magic button that would turn this illness off, most people would say no because of the creativity. But I would says yes.

“If I could relive my life without any of the creativity, if I could turn this illness off and live a quiet life, with a quiet mind, I would.”

He used to hide his illness, living a life of secrecy and shame. As a teenager he “would just go to ground or go to my room and ride it out. Until I was in my 40s, I just felt so alone with it.”

Ottley spent the first 11 years of his life in Papua New Guinea at a time when the country was becoming increasingly dangerous for Australians. When he was nine he was sexually assaulted by a man, a trauma he believes may have triggered a genetic predisposition to bipolar disorder.

“The way it’s explained to me is that you basically inherit a number of genes that – when they are switched on – you start to experience the illness. It can be trauma that switches those genes on.”

In the following decades, whatever he tried, his illness would be waiting to grab him and drag him down. He would become unwell, crash and burn and run. He failed school – “I just couldn’t do it” – and followed his father and brother into the bush to work as a stockman, but says he “was not good at that sort of work”. He studied at Julian Ashton art school, became unwell, went bush again. Returning to the bush became “a pattern”. He studied music at Wollongong University, but couldn’t complete that either. “I actually don’t have any educational qualifications,” he says.

Ottley also has synaesthesia, a neurological condition. “Sound starts to become very colourful and I see lots of shapes, and start becoming hypersensitive to sound and light.” In a rehearsal with musicians he can tell if someone is a bit off-key, “because it is the wrong colour”.

The Tree of Ecstasy and Unbearable Sadness had its genesis in two periods of illness. During a severe episode in 2010, Ottley lost the ability to understand speech. But music was “crystal clear,” he says, “so I started writing music”.

“The sound I was hearing was 97 instruments. I wanted a string family of 50 players, a bass clarinet, a bassoon.” This would become the overture to the symphonic soundtrack to the book, with tumultuous crescendos falling to wailing laments; recorded by the Brno Philharmonic Orchestra and the 40-voice Czech Philharmonic Choir of Brno, it is the sound of psychosis.

“If you start creating an orchestral sound in your head and you’re becoming unwell and you tip into psychosis, you can actually hear it like it’s out there. It’s a 68-part fugue that is meant to represent the clamour of noise in a person’s head, whether it is multiple voices or any other kind of auditory hallucination that is happening, and just becomes unbearable and you just want it to stop.”

A couple of years later, keeping a recovery journal after another serious episode, he wrote the poem which would become the text of The Tree of Ecstasy. “It just sort of dropped out of the universe.”

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The music took two years to compose, and the 74 artworks took three years to paint. Together it is a towering work for adults and children; a luminous, intense and ultimately beautiful journey through the stages of psychosis, and out the other side. “I wanted to create a metaphorical experience that goes straight to the emotional centres, to give people a visceral experience of what it feels like,” Ottley says.

“I think the arts are a direct conduit to our deeper emotional thinking that bypasses logical, superficial thinking, and can get right at the heart of what we feel about something.”

Ottley’s aim is to destigmatise mental illness, to illuminate the experience of those who don’t live with bipolar disorder and advocate for those who do. “Probably the message is that it cannot be about judgment,” he says. “I think all things can be achieved through empathy. I encourage people not to feel humiliated about those aspects of their life, or the thoughts they have around self-harm or harming others. To be really, really open from a very early stage about these things. Because of the deep shame that surrounds these things people just remain closed until it is too late.

“You can get a diagnosis, you can get treatment. Go out into the world and find the people you need to talk to, and ask for their forgiveness for your behaviours, and forgive yourself as well. The condition doesn’t go away, but life goes on and you can find peace.”

Creativity has always been Ottley’s salvation – “I could always turn to that” – but it is the love of his partner and friends that has brought him to relative tranquility.

Likewise, his book ends with his protagonist hearing the distant voices of those who loved him calling him back.

“I am here” he called. And so he came back into the world. And still the Tree of Ecstasy and Unbearable Sadness was within him. And still it grew flowers. And still it bore fruit.

• The Tree of Ecstasy and Unbearable Sadness it out now through Dirt Lane Press. The animation will be screened on 23 June at the University of Sydney, on 18 and 21 August at the National Portrait Gallery in Canberra, and on 21 and 22 September at the State Library in Perth