Towards the end of my last relationship, I acquired a portable speaker. The timing was fortuitous: there was little opportunity for it to become attached to happy or sad memories from my coupled life. It was one of the few shared objects I kept. And, though it felt awkward to walk away from our decade-long home with what looked like a black box, I was ready to start afresh with it.

In my single life I learned the perks of having a speaker of one’s own. An empty flat with an Ikea mattress and a secondhand fridge might seem dispiriting – until the right Wong Kar-wai soundtrack brought out its indie quality. Space Oddity took the edge off slow wifi days. And Talking Heads’ Psycho Killer lent a certain je ne sais quoi to confrontations with inner-city cockroaches. It was nice to know that however grim things got I could still take charge of the ambience of my life.

About the same time, I stopped writing in my diary. Rumination after heartbreak was draining and I couldn’t bring myself to repeat the same loop on the page.

Instead I became preoccupied with finding more music to fill my home. It was a season of expansion. I saved songs I heard while travelling, at parties, in bookshops and cafes. There were tracks I saved because of a band’s name (Clams Casino); a single resonant line (“Give me everything I ever need, or just enough so I can go to sleep”); or feelings that I aspired to (meditative; calm; wildly joyful) but couldn’t summon. It was thrilling to forage for different sounds from the outside world and feel I could change a mood at will.

Soon I began archiving the music in monthly playlists. Sometimes the lists were short and nostalgic and made of songs I already knew. Others were full of new tracks that sent me down a rabbit hole of other discoveries.

In those single years I thought often of a quote from Anne Carson’s essay The Gender of Sound: “Every sound we make is a bit of autobiography. It has a totally private interior yet its trajectory is public. A piece of inside projected to the outside.” I thought of the way my speaker bore witness to an utterly private autobiography. How there was satisfaction in projecting whatever sound I wanted and hearing a specific mood – visceral like a craving for salt or the sharpness of lemon – reflected back at me.

While I could never bring myself to reread any of my diary entries, there was pleasure in revisiting some of the old playlists. Partly because they were records made without much self-consciousness. But more than that, they were a kind of note-taking that distilled the days into moods. When I listen now to the songs from any given month, I can tell whether I felt hopeful or glum, what TV shows or films I was obsessed with and, occasionally – when there were bands that didn’t belong to my own taste – who I might have been dating at the time.

I didn’t anticipate just how potently individual songs could summon past experiences. I can’t listen to Colleen’s November without reliving a particular night in Petra, Jordan, walking through the streets with my best friend M. The path was dark, lit only by candlelight; the stars overhead shone outrageously bright. We walked side by side as the song played on my headphones. There was no hint of the sheer sandstone cliffs that surrounded us. Then, all of a sudden, the winding path opened: 3,000 people sat hushed on the ground, as a single flute player stood waiting to perform. The whole texture of the night is now woven into Colleen’s song. Whenever I replay it I am transported back to that moment – not just the walk itself but what it felt like to be in M’s company. Thanks to these time capsules, I find myself never truly alone.

In the years I made my playlists, I went through many headphones but the speaker remained. Together we have lived in two countries and five homes, through singledom and new loves.

For my birthday this year a new speaker the size of a small pound cake arrived in the mail. I’d told a close friend that my ancient machine was dying and, suspecting I may have trouble letting go of it, she took matters into her own hands.

A week later I pulled my new speaker out of its box and sat it on top of the old one like a small totem. Two eras of my life together – no longer just a black box of a time in flux but part of an ongoing autobiography.

• Candice Chung is a freelance editor and writer. Her first book, Chinese Parents Don’t Say I Love You, is out now via Allen & Unwin (Australia) and Elliott & Thompson (UK)