desmosinator

Turn MIDI files into playable music in Desmos. Also can graph images because why not.

Uses Chrome DevTools and Desmos' JavaScript API under the hood.

What does it do?

• MIDI files → Converts notes to Desmos tone() expressions with a time slider. Animate the slider and watch your music play!
• Images → Plots colored points for each pixel. Uses multithreading to go faster (it's Go, what did you expect). Fun fact: you can get any color in Desmos via the JS API.
• MuseScore links → Paste a MuseScore URL and it'll download the MIDI for you (needs dl-librescore via npx).

Install

go install github.com/openlyfree/desmosinator@latest

Usage

Play a MIDI file

desmosinator song.mid

Tips:

• Set the time slider to play indefinitely in Desmos
• For the best view, set the viewport to y: 0 to 140 and x: t-100 to t+100

From a MuseScore link

desmosinator https://musescore.com/some/song

Draw an image

desmosinator image.png

Flags

Flag	What it does	Default
-cs<N>	Notes per expression for midi and Pixels per thread for photos	500
-step<N>	Skips every N pixels for images (lower = more detail, slower)	10
-nv	No visualization for MIDI (just audio, no note dots)	off

Examples

# Smaller chunks
desmosinator -cs200 song.mid

# Higher res image (will take forever)
desmosinator -step5 image.png

# MIDI without the visual note plot
desmosinator -nv song.mid

How it works

Opens Desmos in a browser (via rod), then injects expressions using Calc.setExpression(). For MIDI, it creates a t slider and a bunch of tone(freq, volume{start<t<end}) expressions. Animate the slider and you get music.

Requirements

• Go 1.21+
• Chrome/Chromium (rod will find it)
• npx if you want to use MuseScore links

Notes

• Drums (MIDI channel 10) are filtered out because Desmos can't really do percussion
• Large MIDI files = lots of expressions = Desmos might chug a bit yk js a teensy tiny bit
• Images are plotted point by point so... be patient
• The progress bar is a bit wonky, it's like half a feature
• There may be no examples but just know that they worked some at point in time
• the thing used to play music from musescore(dl-librescore) is a little weird

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yes i named it desmosinator