Rock, jazz or pop? The science of sound that sorts every song and music genre
You know a song's genre before you know the song. Press play, and within a heartbeat, long before the first word arrives, your brain has
You know a song's genre before you know the song. Press play, and within a heartbeat, long before the first word arrives, your brain has already figured out the music genre: this is metal, this is a ballad, this is a dance floor at midnight. Nobody taught you to do this, and you could not explain how you did it. We tend to assume that recognition is a matter of taste, or culture, or the music we happened to grow up on. It is really something far more physical. Read Full Story Underneath every genre label sits a set of numbers: how rough the sound is, where its energy lies, how squashed its loudness is, how the beat leans, and how long each note takes to fade. Shift those numbers and a song slides from one genre into another, even if not a single word of the lyric changes. In this instalment of Science of Sound, we follow the handful of physical quantities that separate one Western genre from another, analysing famous songs and films for each, and then arrive at the harder question of where the physics runs out and something else takes over. THE INGREDIENTS EVERY MUSIC GENRE IS BUILT FROM Before music splits into styles, it is all the same raw material. A note is just air vibrating. How fast it vibrates is what we hear as pitch, high or low. How hard it vibrates is what we hear as loudness. A quick distinction. A tone is a single, steady sound at one pitch. A note is that same sound once music gives it a name and a place, like Sa, or C. Every note is a tone which is put to work in a piece of music. Now the interesting one. A flute and a guitar can play the exact same note at the exact same volume, and you still know instantly which is which. That difference is called timbre, said tam-ber, and it simply means the colour of a sound. Timbre comes from harmonics. When any instrument sounds a note, whether it is a plucked string, a blown pipe or a struck drum, it does not make a single clean tone. It makes the main note plus a stack of much fainter notes ringing quietly above it. Every instrument lights up a different pattern of those faint notes, and that pattern is its fingerprint. Pitch, loudness, timbre and the faint harmonics ringing above every note are the raw materials from which all music is built. (Photo: Unsplash) Harmonics, then, are those faint higher notes that ring automatically above the main one, and the particular mix of them is what gives each instrument its own voice. It is why a trumpet and a violin never sound alike, even on the same note. Musicians have their own famous list of the building blocks of music, usually seven. Melody, the tune you can hum. Harmony, the extra notes stacked underneath it to fill it out. Rhythm, how the sound is arranged in time. Dynamics, how loud or soft the music gets. Timbre, or the colour of the sound, which we just met. Texture, how many layers are playing at once, a single voice being thin, a full orchestra thick. And form, the overall shape of a song, its verses and choruses. That is the whole toolkit. Every genre is built from these same pieces. What makes rock sound nothing like jazz is simply which pieces each one pushes hardest. ROCK AND METAL: THE VIOLENCE IN A GUITAR STRING Rock's signature is distortion, and distortion is a physical accident turned into a style. A guitar string on its own produces a smooth, rounded wave. Feed that wave into an amplifier and push it harder than the amplifier can handle, and the amp simply cannot reproduce the tallest peaks. It flattens them off. The rounded wave becomes almost a square one, and squaring a wave automatically manufactures a tall stack of new harmonics that were never in the string. The note stays the same, but the sound around it turns dense, bright, and aggressive.
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