About us

La Capseta de Música is made by one person, with the help of a few artificial intelligence assistants. Each assistant has a craft and written rules it must follow. The AIs propose and build; the decisions, the judgement and the final approval always belong to a person.

The Capseta Project

"The Capseta doesn't perform music; it tells memories"

It was born from a grandson, a music box and a memory: my mother's little jewellery box, shaped like a grand piano, from which a ballerina rose to the music of The Nutcracker. When my grandson was about two, I gave him a wind-up music box. It didn't play The Nutcracker but Sol, solet. The problem was that he couldn't make it work yet. He couldn't: his little hands were too small and he didn't have the knack yet. And, like the Blues Brothers, I saw the light: the music box could be digital and live inside a phone. An app that sounded like a music box and kept him entertained.

The first music box was the final project of a postgraduate course in mobile app development that I took at the UPC. It ran on Android and was free. It got 400 downloads in a few months. Now we've developed the idea for iPhone (and iPad), and adapted it to age groups (babies, toddlers or children), each with its own songs and pictures.

The music boxes aren't games. There are no scores, no records, no challenges. They are musical pastimes for young children: just the pleasure of listening to traditional Catalan music, in the public domain, while a picture moves slowly. At most, tapping on the picture. No data, no ads, no purchases. We don't want anything to distract the child while they listen to the songs and watch the animations.

All the resources (pictures, songs and animations) are our own: we made them ourselves, with the help, of course, of a few AI assistants. There's nothing "mass-produced" or "commercial". Many children's apps repeat a rather small set of songs. Everyone wants to sell everywhere, and they think that by taking a dozen "international" tunes they can get by. They think: "It's for kids, no need to make an effort, let's make it generic". That's not our point of view. Our songs are from here, and they've been prepared for each age group, with the utmost care.

Who I am

"Life is software"

I'm Lluís Suñol, a systems engineer from the Barcelona School of Informatics (UPC). Software has always been my life, my passion. I love making software almost as much as playing baseball. But, because of age and health, which don't help, I've stopped playing baseball. I can still make software, though, especially now that I have the help of some fabulous colleagues: my AI assistants.

With some colleagues I co-founded a financial software company, valuing the portfolios and assets of collective investment institutions. My part was the calculations: what allowed these institutions to pass the supervision of the Bank of Spain and the Spanish securities regulator (CNMV), especially for derivatives, the instruments that are hardest to manage and that the supervisor watches most closely. My field has always been calculations and interpreting regulations: laws, notices and circulars from the regulator that forced our clients to change the way they operated. In short: they forced us to change our software.

But life doesn't always take us along smooth paths; sometimes it throws you off a cliff: a few years ago I was diagnosed with fibromyalgia and I had to stop working. Full stop. I'm still on the company's board, which is doing quite well, but far from day-to-day production. And it's not the same. I need to "write code" and, since I can't sit still, I went back to university to keep studying. La Capseta lets me "work" on what I love most: software, music and small children.

And what Claude, who works on it every day, says: "He wants things simple and in their right place. If a name doesn't say what it is, he changes it; if an answer is long, he cuts it. He has the whole app in his head, works layer by layer — going fast is going slower — and asks to be contradicted, but when he is right he doesn't let go. Before talking about technology, he thinks of the crying child and the mother holding him on the underground. On rainy days he arranges lullabies."

Claude, the engineer

Claude, by Anthropic, is the software engineer, the job Lluís has done all his life. It started by gathering the requirements, and from there did the whole design: the parts of each app, how they talk to each other and what happens when something fails. "The music box never breaks" is its rule: if a resource fails, a spare one takes its place and the music carries on.

Now it writes the apps' code and checks every picture, animation and song before it goes into a music box.

ChatGPT, the arranger

ChatGPT, by OpenAI, is the music arranger, working with the MusicXML format. It starts from a well-known song and makes versions of it for each age: slower and simpler for babies, and livelier, with more variations, for older children. The melody is always recognisable; what changes is how it develops, and how it ends. And we try to repeat the chorus as many times as possible.

It works with the Music Seal, and every version is listened to before it is approved: what counts is how it sounds, not how it looks on paper.

ChatGPT, the illustrator

ChatGPT is also the illustrator. Pictures are very important, and Lluís can't draw, let alone digitally. He knows what he wants and explains it in detail, but he's unable to draw it.

All the pictures are its own. It works on Lluís's briefs: it proposes two or three ideas for each brief, recommends one and draws nothing until Lluís says "go ahead". Every picture has a music box with its crank, and is designed for the eyes of a small child: one clear main figure; everything is smiles, nothing scary. Few or many characters, few or many details: it all depends on the audience it's meant for.

Before handing over a picture, it checks it point by point against the Visual Seal.

ChatGPT, the animator

And the animator: it decides how each picture moves. Animations are what bring La Capseta to life. Music, pictures and animations are the heart of our apps, and they go together.

It explains them with everyday comparisons ("it rocks like a cradle") and, once Lluís chooses, writes them in a format the app understands. The movement is always slow and predictable, returning to where it started and never going beyond the limits for each age.

Animations don't depend on any particular picture: any movement works for any music box.

Perplexity, the preparer

Perplexity helped prepare the profiles of all the assistants: each one's craft, what it may and may not do, how it works with Lluís and how it checks its own work. These are the rules that make them all work the same way. It's a kind of external auditor: it proposes the limits of each assistant.

Our rules

Every music box follows two sets of rules that all the assistants must respect: the Music Seal (how they sound) and the Visual Seal (how they look and how they move).