My brother is minimally verbal. He taught me that language is far more than mere words | Rhiannon Lucy Cosslett

I have long thought that each family has its own unique dialect. A panoply of words, references and turns of phrase that would be incomprehensible to any outsider. It is something that comes out of shared history, of childhood misunderstandings and practical jokes. And it exists even when one among you doesn’t talk or, in my brother’s case, is minimally verbal.

My brother is autistic and pronounces things differently, or uses certain stock phrases, and over time these utterances too have become part of the fabric of our conversations. “Pass me the truckrot,” I might say to my mother, meaning chocolate. “Nos da, Cwac,” (literally: “Night, night, Cwac”) my dad will say, borrowing a line from one of my brother’s favourite Welsh-language cartoon catchphrases. It would seem bizarre to you to hear me say “tradoos” instead of “trousers”, but it is a legitimate entry in the family glossary. It’s also a way of communicating with my brother, as well as acknowledging and paying tribute to his unique phraseology.

This wasn’t a phenomenon to which I had ever given much thought until I encountered Ruby Colley, a composer, violinist and sound artist whose brother, Paul, is neurodivergent and non-speaking, with high support needs. In collaboration with Paul, Ruby (who is also neurodivergent) has created a new composition for vocal ensemble, electronics and violin: Hello Halo, which is to be performed in London and Liverpool by the Exaudi ensemble. “When you have one person who speaks and the other doesn’t, the connective conversational flow feels like it’s one-way traffic,” Ruby tells me. “What I really wanted to do with this project was to find that point of connection between the two of us, basically, and bring out all of these details in Paul’s communication style.”

Like me and my brother, Ruby and Paul – they are 41 and 43, respectively – grew up in a house full of music. Ruby began playing violin at the age of three when one of the many volunteers helping two-year-old Paul meet his developmental milestones remarked that the little girl needed something to do. Paul used to sit on the floor, rapt, while she practised. There’s a lovely moment in the short film that has been made alongside the piece – to be released once it has premiered – where Ruby plays the piece to Paul and he starts to smile in recognition and appreciation.

The affinity that many autistic and neurodivergent people have for music, as well as its therapeutic benefits, is well established. Musician James Cook’s memoir, In Her Room: How Music Helped Me Connect with My Autistic Daughter, documents how he used his voice and guitar to communicate with Emily, his non-verbal little girl.

And in his upcoming memoir, Maybe I’m Amazed, my colleague John Harris writes of how songs became a shared language between him and his autistic son, James. John writes of how he fixated on “why chords, tones, rhythms and all the rest sometimes evoke and crystallise emotions and experiences far more powerfully than language, and why working out and performing songs with my son – I play guitar; he tends to focus on bass and keyboards – began to feel like a substitute for conversation. And then I realised something even more remarkable: that it was conversation.” Music, these families discovered, can create “worlds without words”.

Ruby’s piece pays tribute to another such conversation, as well as to her family’s own unique glossary. One of the words Paul likes to say is “hello”, hence the title, and the piece also uses some of the childhood words that he has lost, and the words he uses for important people in his life, including support workers. “In one of the movements there is a reference to Twinkle Twinkle Little Star, a favourite when he was little and something I played all the time when I was learning. Years later suddenly he sang it in the back of the car, pitch-perfect.” It was, Ruby says, a lesson in how Paul understood far more than his family realised.

Hello Halo is timely, coming as it does at a time when verbal neurodivergent people’s voices are becoming more and more prominent. This is obviously a good thing, but it has meant that autistic and disabled people who are non-speaking or minimally verbal, with high support needs, are seeing their stories become increasingly absent from the public conversation around autism. Hello Halo is a reminder that the connection between non-speaking people and their families transcends words. It also makes a firm case for the need for artistic expression for all. Ruby and Paul’s mother, Kate Adams, is the CEO of Project Art Works, which has helped many disabled, autistic and neurodivergent people engage in artistic practice.

“It feels important to say that Paul is an enigma,” Ruby says. “As much as a sister can know her brother through shared experiences, sibling connection and intimate historical knowledge, the gulf of the unknown can be wide. We have learned as a family to accept this element of his unknowable mystery. It’s a surrender that is also an act of love.”

Hello Halo will be performed at Kings Place, London, on 1 February and at Liverpool Harmonic Hall on 3 February

• Rhiannon Lucy Cosslett is a Guardian columnist