A Yokai's First Note — What Yokai Music Is, and Why I Built It

"A major third is four semitones."

That takes about three seconds to memorise. But once you've memorised it and put on any song at all, you still can't hear where the major thirds are. I repeated that loop for a long time: buy the book, underline the terms, learn the vocabulary, close the book still unable to hear a thing.

The books weren't the problem. The problem is that words can't stand in for sound. Almost every item in music theory is, underneath, a claim that something sounds a particular way — and on paper there is no way to check the claim. An unchecked claim isn't knowledge. It's memorisation.

So I started building the missing half: tools that let you hear the sentence you just read, without leaving it.

Six rooms

Yokai Music isn't one app. It's six modules, each aimed at a different kind of "I can't hear it."

SynthLab is about how sound itself gets made. Why a saw and a square feel different, what actually disappears when you close a filter, why lengthening the attack changes an instrument's whole personality. Turn the knob and the explanation becomes unnecessary. A working synth and a sequencer studio sit alongside the lessons, so what you learn goes straight into something you can play.

Chord Lab is a workshop for chord progressions. Place one chord and it tells you what could come next — and why, in those terms: a perfect cadence, a secondary dominant, a borrowed chord. Then it does the part that eats the most time: it voices both hands for you. Keeping a left-hand bass and a right-hand voicing moving smoothly inside an octave is tedious work for a person and fast work for a machine. Export the result as a MIDI file and carry on in whatever DAW you already use.

Theory Lab takes scales, intervals, chords and harmonic function one idea per screen. You move through the slides, press the keyboard, and the thing you just read makes a sound. It's built as the other half of this blog's theory series.

Open Theory Lab — one idea per screen→

Rhythm Lab covers how rhythm is assembled, from beats and bars up to grooves. Then it asks you to write down what you hear on a step grid. Dictation is brutally honest: the gap between what you thought you knew and what you can actually hear shows up immediately.

Ear Trainer is the game. Identify single notes, chords and scales by ear — played with real instrument timbres: piano, electric piano, violin, guitar. Train only on sine waves and sine waves are all you'll ever recognise.

The sixth room is this blog.

What the writing is for

There's something the tools can't do. A tool can show you that something sounds a certain way, but not why people ended up wanting that sound. That's history and context, and it belongs to prose.

So three kinds of writing collect here.

The theory series — why the idea is needed first, then the facts kept short, then a link into Theory Lab so your ears get the last word. It starts with why do-re-mi sits where it does.
The history series — the conditions jazz and hip-hop were born into, and what made them sound the way they do. Mostly by following the instruments and the technology that changed them.
Making-of notes — the nights a single synth patch swallows the dawn, a waveform stumbled upon by accident, and the things I got wrong on the way.

The writing and the tools point at each other. Read about an idea and a link opens the lesson for it; play with a module and there's a way back to the piece that explains it.

Why the browser

No install, no login, no payment. One link opens it.

That's a design decision, not a preference. If pressing "hear it for yourself" in the middle of a paragraph meant creating an account and downloading software, nobody would press it. When checking costs more than about three seconds, the check doesn't happen — and without the check you're right back to memorising. Sound has to arrive within three seconds of the sentence.

Everything is synthesised in the browser with the Web Audio API. The real-instrument timbres come from openly licensed sample sets, and the sources and licences are listed on the about page.

One rule

Nothing half-built ships.

Buttons labelled "coming soon", knobs that do nothing when you turn them, placeholders marked "this is just an example" — leave enough of those around and you don't have a site, you have a construction yard. A module opens when it's usable; a piece gets written when there's something to say. And when I don't know something, I say so.

Sound is more honest than words. So around here, the words try to keep pointing back at it.

Take a look at the six modules→

— YokaiMSG