Most of the data in your product probably lives on a timeline. You just don't show it that way. You scatter it across tabs.

I worked that out today on a Sunday, while trying to close a few hundred of my own.

I save links from newsletters and never read them, so I sat down to clear the backlog. One was called "Happy Map" from The Pudding. No memory of why. I Googled it.

A Google search for the Happy Map URL showing four results, including The Pudding and a Maps Mania blog post.
Where the rabbit hole started. One saved link and a search.

The search alone was a small rabbit hole. The first result was the map itself. The second was a blog I'd never seen, Google Maps Mania, with a post called "The Map of Human Happiness." I clicked that.

It explained the project. The Pudding took a 2017 study where 10,000 people shared their happiest moments and turned the data into a fantasy map. Each moment is a tiny figure. Similar moments cluster into islands: family, hobbies, sensory pleasure. The clever part is the compass. Instead of north and south, the map runs on immediate vs long-term happiness and more vs less agency. Your favourite meal sits near the top. A hard-won degree sits near the bottom.

The Pudding's Happy Map, a fantasy landscape dotted with illustrated people, explaining it is built from a 2017 study of 10,000 happy moments.
10,000 happy moments, drawn as a world you can walk through.

I like a good blog, so I kept scrolling. That's where I hit another post: "Metro Music Maps." I opened the site it pointed to Metro Music or "LA Metro: Ambient" made by Jack Weiss.

The Maps Mania blog post 'Metro Music Maps', showing New York subway lines glowing like coloured strings on a black background.
The Maps Mania post that nudged me from happiness to transit.

This one made me put headphones on.

It's a calm map of Los Angeles that plays music from live transit data. Every time a train reaches a station, you hear a note. Trains on the west side pan into your left ear, the east into your right. Each line gets its own instrument. Roll into Union Station and a little bronze chime fires. There's a "Conductor" panel where you can mute a line, change its sound or shift the whole key. When I landed, it was set to Morning Rush, in D Dorian.

The full Metro Music screen showing the Los Angeles map in Morning Rush mode with live trains and station arrivals.
Every train arrival is a note. This is Morning Rush, in D Dorian.
The Los Angeles metro map with a tooltip labelling the blue A Line as a three-car light rail train.
Hover a train and it tells you the line and what's running.
A list of upcoming Metro station arrivals with line and destination, such as Vernon to Long Beach.
Each row is a real train about to reach a station.
The Metro Music side panel listing live vehicles, current listeners and the colour key for the A to J lines.
The live legend: vehicles running, people listening, a colour per line.
The Conductor control panel for choosing a musical key, a time-of-day scale, event sounds and an instrument for each line.
The layers are editable: a key, a mood, one instrument per line.

Metro Music pointed me to Train Jazz, which I'd played with months ago and forgotten. New York this time. About 800 real trains play as one jazz band: the 1/2/3 from 1904 on upright bass, the busy 4/5/6 on a Rhodes piano and you can flip the map into a music-sheet "bars" view.

The full Train Jazz music-sheet view with every subway line as a stave and a playhead sweeping across.
Flip the map into a music sheet: 1/2/3 on upright bass, 4/5/6 on a Rhodes.
Train Jazz in its music-sheet view with the red 1 line highlighted across the top stave.
Each line is a stave; each train is a note crossing it.
The Train Jazz intro screen describing how about eight hundred real subway trains form a jazz combo.
Train Jazz, before you press play.
Train Jazz music-sheet view with the green 6 line highlighted and sixteen trains running.
Highlight a line to pick out its part in the band.
A Train Jazz note explaining that the 1, 2 and 3 lines from 1904 play the upright bass.
The oldest lines: 1/2/3, from 1904 carry the upright bass.

So there I was. Two tabs. Two cities. Both turning trains into music. And it hit me: this is Julian Lehr's "Multi-layered calendars" just sung instead of drawn.


Layered Time Design

Here's Julian's point in my own words.

A calendar shouldn't be a grid of identical blocks. Time should be the base rail. On top of it, you stack layers. A meeting is a layer. The travel to it is another. The tasks for it are another. You can stack past layers too: what you played, how you slept, how stressed you were.

No single layer is the point. The point is seeing them together. I've started calling this Layered Time Design. And once you see it, you see it everywhere. The metro-music maps are doing the same thing, they just swap your life for a city and calendar blocks for sound.

Two examples make it concrete.

Your calendar. The rail is your day. The layers are meetings, travel, tasks, sleep and old data like music or health. Alone, each is a bit dull. Together they show patterns: "I'm more stressed on days with bad sleep and back-to-back meetings." You'd never catch that in one layer. You catch it when they share a timeline.

The metro-music maps. The rail is the live schedule. The layers are where each train is, which line it belongs to, where it sits on the map, the time of day and special stations. Alone, each is just data. Together, they're a song of the city. You can hear how busy it is. You can hear where you are, because the trains nearest you grow louder.

Your calendar Metro-music maps
Base rail Your day / week Live transit schedule
A layer Meetings Where each train is
A layer Travel + tasks Line identity (its instrument)
A layer Sleep, music, health Geography (left/right, near/far)
A layer — Time of day
What emerges "Bad sleep + dense meetings = stress" A live song of the city

Julian's multi-layered approach gives you a conceptual frame to see these projects not as clever one-offs but as examples of what happens when you:

  1. Take a rich data domain tied to time,
  2. Treat each entity type as its own layer with semantics and
  3. Build an interface that lets those layers overlap, interact and be reweighted.

Transit data + geography + instruments + your location + time-of-day mode = an experience that tells you :

  • How busy the network feels right now.
  • What your part of the city "sounds like".
  • How different lines contribute to the whole texture.

For calendars, the output is a better sense of how you spend your life. For Metro Music / Train Jazz, the output is a living sonic portrait of a city.

Same pattern, different substrate. One you read; one you hear.

A clean map of Los Angeles with coloured metro lines and dots marking live trains.
Los Angeles, by Metro Music.
Train Jazz showing the New York subway as a grey map with coloured dots for live trains.
New York, by Train Jazz.

And this isn't staying in the browser. Someone's building Metroboard, a mid-century-style wall display of a city's live trains. LA Metro, the real agency, gave Metro Music a public shoutout.

The idea is good enough to jump from a webpage to a physical object and a city's own data feed.



Closing thoughts

I design products, so this is where my brain went. Most products have a time axis hiding in them: a schedule, a history, an activity feed. We just don't treat it as a spine. We scatter the related data across tabs and screens instead.

So, two prompts:

  1. Find your time axis. What is the real time axis in your product? What's the schedule, history or feed that quietly orders everything? Name it.
  2. Pull the layers onto it. What data are you keeping in separate tabs that actually shares that axis? Put two or three of them on the same rail and see what new pattern shows up because the insight is almost never in one layer.

That's the whole thing. The insight was never one layer. It was the stack.

I opened a tab to find a happy map. I closed it having found a song and a sharper way to look at my own work. Not bad for a tab-cleaning Saturday.