Absolute pitch — the rare ability to identify or produce any note by its name alone, with no reference point — gets most of the popular attention, but it's not actually the ability that lets most trained musicians function. Far more common, and far more trainable, is relative pitch: the ability to recognise the distance between two notes, called an interval, regardless of what the actual starting note happens to be. It's relative pitch, not absolute pitch, that does the heavy lifting behind recognising melodies, transcribing music by ear, and singing in tune.
An interval sounds the same no matter where it starts
An interval is simply the distance in pitch between two notes, and crucially, that distance has a consistent, recognisable quality regardless of which specific notes are involved — the interval between C and G sounds structurally identical to the interval between D and A, because both represent the same underlying distance (a perfect fifth), even though the actual pitches are completely different. This is precisely what makes a melody recognisable when it's transposed into a different key: "Happy Birthday" sung a step higher or lower is still unmistakably "Happy Birthday," because what a listener actually recognises is the pattern of intervals between successive notes, not the specific absolute pitches involved.
Training the ear to hear structure, not just sound
Ear training deliberately builds relative pitch by associating each interval with something memorable and consistent — often the opening notes of a familiar song, since many well-known melodies happen to open with a specific, easily recognisable interval (the first two notes of "Here Comes the Bride," for instance, outline a specific interval many ear-training methods use as a reference). With enough repeated practice, a musician learns to identify an interval's characteristic sound directly, without needing the mnemonic crutch, which lets them transcribe a melody they hear, sight-sing a written melody accurately, and recognise chord qualities and harmonic movement by ear — skills central to functional musicianship that don't require, and aren't meaningfully improved by, having absolute pitch at all.
What we're still unsure about
The mechanics of interval recognition and the effectiveness of ear-training methods built around it are well established through both music pedagogy and psychoacoustic research. What remains a more genuinely open question is how trainable absolute pitch itself is, compared with relative pitch — absolute pitch appears substantially more common among people who received musical training at a very young age, within a specific developmental window, and researchers continue to investigate exactly how much of that reflects an innate predisposition versus a genuine critical period for acquiring the skill, without a fully settled answer for why some people seem able to develop absolute pitch as adults and most cannot.
This sits inside Intervals & Ear Training, one of eight topics in Music Theory, one of four domains in Music, one of seventeen subjects the app can quiz you on.