People are once again discussing the mystery of vinyl records, and how they are probably really created by magic. But without invoking wizards, how do vinyl records contain music which can then be played back?
The first ever sound recording was made in 1860 by French inventor Édouard-Léon Scott de Martinville. His device, which he called the phonautograph, was a pretty simple way of recording sound.
"I cover a plate of glass with an exceedingly thin stratum of lampblack. Above I fix an acoustic trumpet with a membrane the diameter of a five franc coin at its small end – the physiological tympanum (eardrum). At its center I affix a stylus – a boar’s bristle a centimeter [0.4 inches] or more in length, fine but suitably rigid," Scott de Martinville explained. "I carefully adjust the trumpet so the stylus barely grazes the lampblack. Then, as the glass plate slides horizontally in a well formed groove at a speed of one meter per second [3.3 feet per second], one speaks in the vicinity of the trumpet’s opening, causing the membranes to vibrate and the stylus to trace figures."
Though this method produced a recording of sound, the problem was it was near-impossible to actually play it. The phonautograph produced a visual representation of the sounds he had made – a frankly haunting rendition of the French folksong "Au Clair de la Lune" – but it took until 2012 for those marks to be decoded and converted back to sound.
A short time later in 1877, Thomas Edison created a device that could record and play back sound. In Edison's "talking machine", or phonograph, sound captured through a mouthpiece moved a diaphragm, which moved a stylus up and down to make indentations in a drum wrapped in tin foil.
The stylus was then run over these indentations, replicating (in terrible quality) the original sound.
Vinyl records are produced in a similar way, though our methods of capturing and playing back sound have significantly improved.
Sounds travel as waves through the air (as well as liquids and solids). Just like with earlier devices, these waves are recorded as physical indents, in this case by a moving needle that cuts grooves into a master record. Using a mold, these indented translations of sound can be put onto other vinyl records,
Playing back a vinyl record involves a needle, usually tipped with a hard material like diamond, going through these grooves. As this happens, the tip moves up and down. Further down the arm, a magnet is inside a coil of wire, moving up and down with it.
This movement of the magnet creates a fluctuating electric current, which is then converted back into sound by vibrating the attached speaker.
Or, you know, wizards did it.