What a cent is
An octave divides into twelve semitones, and each semitone into a hundred cents — 1200 cents to the octave. A cent is far too small to hear as a musical step. It is the unit you reach for once the question stops being which note is this and becomes are these two notes actually the same. Guitar and bass intonation, string bends, choral tuning and the drift of a slightly flat open string all live at this scale.
The cent gap exercise plays two tones back to back and asks which sat higher — or whether they matched. Narrow the gap and the task gets harder in a way that is measurable rather than vague.
How finely can you hear?
Published figures vary a great deal with the method used, so treat any single number with suspicion. One well-known comparison of professional musicians and non-musicians put trained listeners at roughly 8–11 cents and untrained listeners at about double that. Other work, using practised listeners under optimised laboratory conditions, reports musician thresholds down near 2–3 cents. Later reviews land in similar territory.
Two things hold across all of them. The untrained threshold is coarser than most people assume — a gap you cannot hear at all is still a gap a tuner would flag. And it moves: this is a trainable skill, and it improves faster than most musical skills do.
That is the point of measuring rather than guessing. Set a gap, run a round, and the accuracy chart shows where your own threshold actually sits today.
Hearing differences that aren't there
Tone 1 higher, tone 2 higher, or the two were identical. That third answer is the one that earns its place. Without identical pairs you can score well by always hearing a difference, whether or not one is present — a common failure mode, and completely invisible in a single accuracy number. The round summary calls it out separately when the identical pairs are the ones going wrong.
Three answers also means guessing scores 33% rather than 50, so every judgement the app makes about your accuracy is measured against that floor instead of a coin flip.
Intervals and relative pitch
The second exercise plays the tonic, then another note, and asks how far apart they were. This is relative pitch: not naming notes in absolute terms, but hearing the distance between them. It is the skill behind picking a line up by ear, transcribing, and knowing where your hand should go before you play.
The reference is always the tonic, so the key holds and the movable-do solfège syllables keep their meaning — do, re, mi stay attached to scale degrees rather than to fixed pitches. Start with a handful of intervals and add a neighbour once those are solid; a new interval is easiest to learn by contrast with one you already know.
Sing them back. Naming an interval you have only ever heard is a much weaker skill than one you can produce — pitch the second note yourself, out loud, and say the solfège syllable as you land on it (do up to sol, do up to me). Singing forces you to commit to a pitch before you hear whether you were right, which is exactly the muscle that recognition alone leaves untrained.
A useful way in is to anchor each interval to a song that opens with it — the rising fifth of Twinkle, Twinkle, the tritone of the Simpsons theme. EarMaster publishes a free interval song chart generator that lists well-known songs for each one, which is worth keeping open beside this while the shapes are still settling.
Where the notes sit
Trials are drawn from the piano's range, A0 to C8, and you set the span you want to work in. For reference: a four-string bass sounds E1 to about E♭3, a guitar E2 to E6. Both are written an octave above where they sound, which is why an open E on a bass reads as E2 on paper but arrives at your ear near 41 Hz.
Pitch discrimination is not uniform across that range, which is why accuracy is charted against the centre pitch of each pair as well as against the gap. Most people are noticeably worse at the extremes.
How do I improve my ear?
Aim to sit around 70–80% correct. Score much higher and the exercise is too easy to be teaching you anything; sit near chance and there is no signal to learn from. After every round the summary tells you which side of that band you landed on — but it only advises. Nothing changes difficulty behind your back, so the controls below are yours to move.
On the Cent gap tab, the blunt lever is Gap: lower it to make the task harder, raise it to make it easier. Switch Gap type to Range and each round draws a random gap from the span you set, which spreads practice across several difficulties instead of drilling one. Pitch range is the subtler lever. Narrow it to work a single register at a time; widen it to be tested everywhere. The low end is markedly harder than the middle, so the same gap sitting down at A1–A2 is a stiffer test than at A3–A4 — if a gap feels impossible, try it higher up before you widen it.
On the Intervals tab, Intervals in play is the main dial. Fewer intervals means a better chance of guessing right and an easier round; switching one more on makes it harder, and the summary suggests which neighbour to add next. Second note set to Above or below brings in descending intervals, which most people find harder than ascending ones. Octaves in play widens the register the tonic can appear in. Scale selects a whole set at once when you would rather work in a key than pick intervals by hand.
Two habits worth keeping. Change one thing at a time, or you will not know which change moved your score. And hit Reset stats and charts after a real difficulty change, so the charts describe the exercise you are actually doing rather than an average of two. Short, frequent sessions beat long ones — Pairs per round in the preferences sets how often you get a summary.