# 🌈 Chromatic 🎶

## Music, Math, Colour, and Free Software

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![Chromatic](chromatic.svg)

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# What is a note?

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# A sound at a particular frequency

![sine](sine.png)

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# Hz = "cycles per second"

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# What is <big>A</big> note?

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# A4 = 440Hz
aka. ISO 16:1975 
3 pages!

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![iso16-1](iso16-1.png)

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![iso16-2](iso16-2.png)

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# Octaves
2:1 Ratio
A3 = 220, A4 = 440, A5 = 880, etc.

![sine21](sine21.png)

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# What about the other notes?

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# Intervals (from "C4")
(aka: "middle C", aka: "do", aka: ~261.63 Hz)

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# Octave (C and "high C")
2:1 Ratio

![sine21](sine21.png)

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# "Perfect fifth" (C and G)

3:2 Ratio

![sine32](sine32.png)

Looks good!  Sounds good!

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# What sounds good?

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# "Ratios with small numbers"
aka: "just intonation"

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## "Tonic"  — C — 1:1

## "Octave"  — high C — 2:1

## "Perfect Fifth"  — G — 3:2

## "Fourth"  — F — 4:3

## "Major third"  — E — 5:4

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# Tonic, Major Third, Fourth, Fifth, Octave

![Tonic Third Fourth Fifth Octave](cefgc.png)

## 1:1, 5:4, 4:3, 3:2, 2:1

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# ... plus Second, Sixth, Seventh

![D A B](cdefgabc.png)

## 9:8, 5:3, 15:8

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# Full chromatic scale (just intonation)

![chromatic just](chromatic-just.png)

## 16:15, 6:5, 45:32 (diabolical!), 8:5, 9:5

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# Full chromatic scale (equal temperament)

![chromatic equal](chromatic-equal.png)

## $$ note = previous * \sqrt[12]{2} (\approx 1.06) $$

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# Full chromatic scale (comparison)

![chromatic equal](chromatic-both.png)

## ...not bad!

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# The tritone, 45:32

"Diabolus in Musica"

![sine-tritone](sine-tritone.png)

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# Circle of fifths

The coolest ratio is the perfect fifth (3:2 = 1.5)

Stepping by fifths, you hit all 12 notes!

C → G → D → A → E → B → F# → C# → G# → D# → A# → F → C

See also: how to be a cool guitar player.

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## C → G → D → A → E → B → F# → C# → G# → D# → A# → F → C

$$ (3:2)^{12} = 1.5^{12} \approx 129.75 $$

$$ 2^7 = 128 $$

"Pythagorean comma", ~1.36%

So close!!

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CC-BY-SA-4.0 https://commons.wikimedia.org/wiki/User:Cmglee

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Isaac Newton, 1704

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Jim McKeeth - Own work, CC BY-SA 4.0

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Kwamikagami - CC BY-SA 4.0

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Me - LAST-NIGHT-2AM

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![glock](glock.png)

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![boomwhackers](boomwhackers.png)

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![stickers](stickers.jpg)

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# But where can you get music from?

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# "Scratch an itch"

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```python
import sys

for line in open('template.html'):
 if '-- notes --' in line:
 for line in sys.stdin:
 for note in line.strip():
 print(rf" {note}")
 print(" ")
 print(" ")
 else:
 print(line)
```

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```
<html>
 <head>
 <style>
 .note {
 print-color-adjust: exact;
 display: inline-block;
 color: white;
 text-align: center;
 vertical-align: middle;
 -webkit-text-stroke-width: 0.03em;
 -webkit-text-stroke-color: black;
 border-radius: 0.4em;
 padding-top: 0.5em;
 padding-bottom: 0.5em;
 width: 2em;
 }
 .c { background-color: red; }
 .d { background-color: darkorange; }
 .e { background-color: yellow; }
 .f { background-color: chartreuse; }
 .g { background-color: teal; }
 .a { background-color: indigo; }
 .b { background-color: fuchsia; }
 </style>
 <body>
 
 </body>
</html>
```

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```
CCGGAAG
FFEEDDC
GGFFEED
GGFFEED
CCGGAAG
FFEEDDC
```

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![avery](avery.jpg)

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## ...probably this makes sense in javascript.

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## ...and maybe I put it online for other people to use?

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## Life goes on, working my day job, using GitHub

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# FOSDEM 2025

## Keynote by ~Bradley~Karen and Denver

### "The Growing Body of Proprietary Infrastructure for FOSS Development: Repeating Bad History"

### Go watch the video. It's really great.

### Support the Software Freedom Conservancy

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# tl;dr: GitHub is proprietary software

## We're gonna get burned.

## We always get burned.

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# Started seriously thinking about Forgejo

## Decided to use Chromatic (it has a name now!) as a test project

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# Forgejo: software for running a forge
# Codeberg: service provider, using Forgejo
# Forgejo itself is developed on Codeberg
# You can host your own Forgejo instance

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![forgejo.png](forgejo.png)

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# Forgejo tries to be like GitHub

## Web UI, REST API, workflows

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# Forgejo has migration from GitHub

## issues, pulls, labels, milestones, releases, wifi, LFS

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# Forgejo supports SHA256 git repositories

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# Codeberg static page hosting

## https://lis.codeberg.page/chromatic/

### branches: https://lis.codeberg.page/chromatic/@branchname

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# Federation: work in progress

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# Codeberg has (limited) CI runners

## (but for workflows, you need your own)

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```
[chromatic/main]$ cat .woodpecker/check.yaml 
when:
  - event: pull_request
  - event: push
    branch: main
  - event: manual

steps:
  - name: typescript
    image: node:23
    commands:
      - npx --package=typescript tsc
  - name: biome
    image: node:23
    commands:
      - npx @biomejs/biome check
```

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# How is Chromatic looking today?

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![screenshot](screenshot.png)

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# I love PRs!

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# Thanks for coming <3