How is music put onto records?

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How, when pressing vinyl, does music go onto the actual vinyl? I have seen records pressed but, how do they put non digital files onto a record? Before digital music formats.

In: Technology

Vinyl has irregular grooves. When the needle of the player runs through a groove, it wobbles with these irregularities, and this is translated into sound by the player through electrical means.

There are top and bottom pressing master plates which put indentations or grooves on a polyvinyl chloride ‘biscuit’ which gets flattened out to form a specific size and/or colour of a vinyl record.
Depending on the shape and depth of these groves, a different pitch of sound is created when played back via a turntable’s needle running over the specific part of a groove in a song.
The top plate deals with the side A and the bottom with the B side.
As to how the master plates are created [This should help describe the process](https://youtu.be/5OWEEFg6fTY)

You ever seen one of those old gramophones where they speak into the horn, and then crack the wax cylinder back and hear their voice… the way this works is the vibrations caused by their voice pushing and pulling the air back and forth vibrate the horn, and those vibrations move a needle along the wax (this is also how record lathes work today) it literally **etches the shape of the soundwave into the wax** , so that when a needle is dragged against it recreates that soundwave and moves the air in a way similar to the original sound.

Now you need to understand how a microphone works to understand the next bit: condenser microphones basically are capacitors, and like the needle in a gramophone, the sound waves in the air push and pull on a metallic diaphragm (basically a sheet of metal) which is placed opposite another static sheet of metal which is attached to a power-source. The pushing and pulling of the diaphram changes the frequency of the electrical charges traveling down the wire, and if you hook it up to a Speaker which (which again, is a magnet being buffeted by a electromagnetic coil that creates sound vibrations) you get the sound back.

Then in the 1920’s someone invented tape recording. A tape is coated with tiny iron particles, much like a hard-disk drive is today. This runs at speed over a head which contains a electromagnet which when receiving the electrical currents from a microphone rearranges the iron particles, run a passive electromagnet over the particles to ‘read’ it and you can retrieve the sound.

I think it was because of Bing Crosby in the 1940’s that high quality tape recording machines were developed that allowed music artists to record multiple takes. Now you could record several different recordings together, play them at once, and then you could attach it to a record lathe but instead of cutting wax, cut acetate disc – which looks a lot like a vinyl record you’re familiar with. Just like a grammaphone the lathe etches in the soundwave that is produced by the tape into the acetate surface.

The acetate disc then goes through a complicated process I don’t understand which creates an ‘inversion’ or negative called a “press”. So the high ridges which signify the high-pitch but quiet bits become deep, and vice-versa the low ridges which are low frequency but loud become high. Sort of like a photographic negative. This press is, as you know, stamped into the hot wax to mass produce vinyls.

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