Three beats: two are identical, one is off. Find it, then judge how much faster or slower it is. 5 rounds, getting harder.

What Chronfork measures

Chronfork is built around one specific perceptual skill: your tempo just-noticeable difference (JND), the smallest change in speed you can reliably tell apart from a reference. Each round is an oddball task followed by a magnitude estimate. Three short beat patterns play; two share the same tempo and one runs slightly faster or slower. You find the odd one, then judge how different it was. As you keep succeeding, the odd beat's deviation shrinks, so the game closes in on the point where you can no longer feel the gap. Written as a percentage of the beat, that point is a practical, informal read on your personal threshold.

How to play

Each round has two steps. Step 1, find the odd tempo: press ▶ to hear all three beats, then tap the pad whose tempo is off. You can replay as often as you like before committing. Step 2, judge the size: once you've picked the odd beat, rate how different it felt on the five-point scale (a little to a lot, faster or slower) and confirm. There are five rounds, and the gap narrows as you go. Play by ear with sound on, or watch the on-screen pulse if you prefer a visual cue; both carry the same timing. Keyboard users can tab to each pad and activate it with Enter or Space.

How scoring works

Your result is driven by the smallest deviation you still caught correctly. The game tracks the percentage difference between the odd tempo and the reference on each round; when you identify the odd beat and estimate its size well, the next round makes the difference smaller. Your headline "brag" number is the tightest percentage you handled across the five rounds. A lower number means a finer threshold. For orientation, a 5% difference at 120 BPM is about 6 BPM, and 2% is roughly 2-3 BPM.

What your score means

Read the number as a rough band, not a verdict. The ranges below reflect commonly cited tempo-JND findings, so treat them as orientation rather than a fixed grade:

Threshold	Rough interpretation
under ~2%	Very fine, near trained-listener territory
~2-5%	Typical for an attentive listener on a clean beat
~5-10%	A solid everyday sense of tempo
over ~10%	Plenty of room to sharpen with practice

A single round can be lucky or unlucky; the pattern across many days is the honest signal.

Common mistakes

A few habits inflate your threshold. Answering too early, before you've heard all three beats settle, throws away information, so replay first. Over-weighting the first beat of each pattern makes you judge the attack rather than the tempo. Leaning on a visual cue when your audio is muted can mislead you, depending on your screen's timing. And second-guessing a clear first impression tends to drag your answer toward the middle of the scale, so trust the read you got on the first honest listen.

Practice progression

Treat Chronfork as the "detection" rung of a wider timing practice. A workable ladder: (5 min, beginner) play today's round with sound on, replaying freely, and just try to name faster-or-slower before rating size. (10 min, intermediate) commit to a first-listen answer, then verify on replay, to build confidence under less information. (weekly) pair it with tap tempo and the steady-clock plan so detection, measurement and reproduction grow together. Related games: Chronmber (faster-or-slower direction) and Chrondle (spot the odd beat over ten rounds).

The science behind it

Chronfork rests on two well-studied ideas. The first is the just-noticeable difference and Weber's law: the smallest detectable change in a stimulus tends to scale with the size of the stimulus, so a tempo threshold behaves like a percentage of the beat rather than a fixed number of BPM. The second is oddball detection paired with magnitude estimation, a classic psychophysics pairing for probing perceptual limits. Sensitivity to tempo is not fixed: trained musicians detect smaller changes than non-musicians, and thresholds vary with the base tempo and whether you hear a bare click or full music. Our full write-up is in tempo JND & Weber's law.

Limitations

Chronfork is a game and an informal self-check, not a clinical or diagnostic tool. Browser and device timing are not laboratory-grade, so absolute numbers should be read with caution, and results from different devices are not strictly comparable. A single session doesn't establish your "true" threshold; attention, fatigue and audio setup all shift it. And a score here reflects tempo discrimination specifically, not musicianship or rhythm as a whole.

Ready to find today's threshold? Chronfork's daily round takes about a minute: find the odd beat, judge the gap, and watch your number over time.

Play today's Chronfork ↑

Frequently asked questions

What does Chronfork actually measure?

It gives an informal estimate of your tempo just-noticeable difference: the smallest change in speed, as a percentage of the beat, that you can reliably detect. It is a self-check, not a clinical measurement.

Is a lower score better?

Yes. The number is the tightest percentage difference you handled, so a lower figure means a finer threshold, and you can feel smaller changes in tempo.

Why does my score change day to day?

Attention, tiredness, headphones and even the base tempo all move the threshold, and a single round has some luck in it. Look at the trend across many days rather than one result.

Does headphone or device lag affect it?

It can. Bluetooth and some browsers add latency, which is fine for judging one beat against another but means absolute numbers should not be compared across devices.

How can I improve my threshold?

Play regularly with full attention, replay before answering, and pair Chronfork with reproduction practice like the steady-clock plan. Sensitivity tends to sharpen with experience.

Chronfork

About Chronfork: measure your tempo threshold