Those familiar with music know that each conventional music note has a pitch, and each pitch is produced at a certain frequency. We have common frequencies used to define where notes should be played—for example, 440 Hz for a middle A. Since wavelength is equal to speed * frequency (where the speed of sound is 340 m/s), each frequency corresponds to the wavelength of the note. These wavelengths can be reproduced using vibrations, which is how records are able to play music.
The spiral grooves engraved on a record’s surface have physical patterns specific to the waveform of the desired sound. In other words, the grooves are engineered to make the needle vibrate in such a way that it produces the sounds from the original song.
Really early records were made out of shellac and finely pulverized rock. Later on, companies started introducing lighter, more flexible compounds for record manufacturing. Starting in the 1930s, vinyl slowly became the popular compound used for production because of its lighter weight, elastic properties and low ambient noise qualities.
There are three common types of records. 78s were the first to be produced, beginning in the late 1800s with the invention of the gramophone and continuing until the 1950s. “78” refers to the number of rpm at which the record was played, although some records during the time of 78s had other speeds such as 90 or 100. These records usually had one song per side even though they were 10 or 12 inches in diameter.
Because records produce sound physically, most scratches are irreparable since part of the pattern needed to produce the sound has been altered. Records need to be kept clean and handled carefully in order to produce the best sound.
Vinyl records are still played today; you can buy them pretty cheap at places like Exile on Main St. in Champaign or See You Vinyl in Urbana.