Is it free, and do I need to sign up?

All three levels are free and play without an account, in the browser. Rounds run 90 to 110 seconds, meant for one before you sit down to mix.

Why are there acceptable zones as well as a perfect one?

Because instruments occupy ranges, not points. An electric bass has its fundamental in BASS but its definition in LOW-MID, and both answers describe something true. Scoring only one would teach a false map.

Is this useful if I already know what an EQ does?

It's useful if you still have to sweep to find things when you open one. Knowing what a filter does and knowing where to look are different skills; this is the second, and it's the one that saves time every session.

What's the next step once I'm good at it?

EQ Surgeon: there it's no longer about which zone an instrument lives in, but about hearing the specific curve someone applied to it.

Frequency Drop: recognise the 7 zones of the spectrum by ear

A map of the spectrum in your head

There are two ways to work in front of an EQ. One is moving things until it sounds better, which works sometimes and teaches nothing. The other is hearing the problem, knowing which zone it's in, and going straight there. The difference isn't talent: it's having a map of the spectrum internalised enough that «where is that?» has an answer before you touch anything.

Frequency Drop trains that map by association rather than memorisation: it hands you an instrument and you drop it into its band. There are 7 zones — SUB-BASS (20–60 Hz), BASS (60–250 Hz), LOW-MID (250–500 Hz), MID (500 Hz–2 kHz), HIGH-MID (2–6 kHz), HIGH (6–12 kHz), AIR (12–20 kHz) — and 15 instruments, from kick to shaker, and the point is that after a few rounds you stop thinking in numbers and start thinking in places.

Almost no instrument lives in a single place, and the game reflects that: every card has one perfect zone and several acceptable ones. A snare has its body low and its crack in MID (500 Hz–2 kHz); a piano has the widest range of any instrument here, which is why it accepts four different zones. Hitting the perfect zone scores more, but a reasonable answer doesn't sink you — because in a real mix it wouldn't either.

How to play, step by step

1.Pick a level. What changes isn't speed: it's which instruments enter the deck. Apprentice only drops the obvious ones; Engineer brings in pads, strings and backing vocals, which are the ones people genuinely confuse.
2.An instrument card falls. Below it are the 7 zones of the spectrum, each with its range written out: from 20–60 Hz up to 12–20 kHz.
3.Drop it in the zone where its main energy lives. If you're unsure, ask which part of the sound you're hearing: the body or the attack.
4.The perfect zone scores full; an acceptable one scores partial; a wrong one scores nothing. After each card you see its real range and, on several, a note on why it lives there.
5.At the end of the round you get a label based on your score: Apprentice, Student, Mix Engineer, or Frequency Master from 8,000 points.

What each level includes

ApprenticeFree: Only instruments with an unambiguous home: kick and bass in BASS, hi-hat and cymbals in HIGH. This is the round for pinning down the extremes of the spectrum, which is where to start.
AssistantFree: Vocals, snare, electric guitar, acoustic guitar, piano and shaker come in. Here the first real problem appears: several different instruments share MID, and you have to decide which weighs most.
EngineerFree: Backing vocals, synth pad, organ, strings and sub bass are added. It's the full deck and the one that actually teaches, because these are the timbres that step on each other in a mix.

Four shortcuts that work

Think of body and attack separately. Almost every instrument has its body one or two zones below its attack: the snare's body sits low and its crack in MID (500 Hz–2 kHz).
SUB (20–60 Hz) is the zone you feel before you hear it, and the one cheap headphones reproduce worst. If a laptop speaker gives you nothing, it isn't your ear failing.
HIGH-MID (2–6 kHz) is the most expensive zone to get wrong in a real mix: presence and intelligibility live there, and so does fatigue. Worth nailing before AIR.
When torn between two adjacent zones, pick the lower one. Most beginner errors go upward, because the attack is what grabs attention first.

Frequently asked questions

Is it free, and do I need to sign up?: All three levels are free and play without an account, in the browser. Rounds run 90 to 110 seconds, meant for one before you sit down to mix.
Why are there acceptable zones as well as a perfect one?: Because instruments occupy ranges, not points. An electric bass has its fundamental in BASS but its definition in LOW-MID, and both answers describe something true. Scoring only one would teach a false map.
Is this useful if I already know what an EQ does?: It's useful if you still have to sweep to find things when you open one. Knowing what a filter does and knowing where to look are different skills; this is the second, and it's the one that saves time every session.
What's the next step once I'm good at it?: EQ Surgeon: there it's no longer about which zone an instrument lives in, but about hearing the specific curve someone applied to it.

Where to go next

The full map, band by band with each zone playable, is in the frequency ranges guide. What to do with what you find is in the EQ guide, and the week-by-week plan for the whole ear is in train your ear. Once it's clear, the next exercise is hunting the exact frequency by ear in EQ Surgeon.