Edison’s phonograph was the first machine to both record sounds and play them back. Edison arrived at the invention through his work on the telephone, independent of the work of Edouard-Léon Scott de Martinville and Charles Cros. While Scott was the first person to record sound and Cros was among the first to suggest playing it back, Edison approached sound recording and sound playback as two necessary aspects of the same endeavor.
When Edison began his experiments to make patentable improvements on Alexander Graham Bell’s telephone, he brought with him many years of experience with telegraph equipment. In fact, he initially referred to the telephone as a “speaking telegraph;” to him it was just another way to send signals over a wire.
Telegraphers had long recorded incoming signals as dots and dashes on paper tape. An operator who was too busy to receive a message could record it and play it back later. He could also play it back at a slower speed to increase the accuracy with which he translated the dots and dashes into letters written on paper. On very busy lines he could transmit the recorded message at a much faster speed to a distant station, where it would be re-recorded and played back at a more human speed for the distant operator to write to paper.
Telegraph messages were typically transcribed in real time by an operator listening to the dots and dashes clicking on a sounder. But commercial telegraph stations also allowed for the recording of incoming messages onto paper tape and for the playback of those messages for transcription or retransmission. Three images to the right illustrate how this worked. The simplest mechanisms (top left) wrote dots and dashes on moving strips of paper, to be read by the operator at his convenience. The message could also be perforated into the paper (top right), and later played back to the sounder or retransmitted (bottom), often at a much higher speed. The "Morse Telegraph Station" image above shows a fully equipped telegraph station with recording device in place.
In this way, Edison was no stranger to recording and playing back electrical signals for the purpose of time-shifting (playing back later) and time-compressing (playing back fast). His Embossing Translating Telegraph, designed in 1876 and built early in 1877, is a beautiful example of a telegraph recording and playback machine.
So it was a natural progression for Edison to explore how best to record telephone signals, like telegraph signals, for all of the same reasons. By mid-July of 1877 he was convinced he could do so:
Just tried experiment with a diaphragm having an embossing point and held against paraffin paper moving rapidly The new speaking vibrations are indented nicely and there’s no doubt that I shall be able to store up and reproduce automatically at any future time the human voice perfectly reproduced slow or fast by a copyist and written down.
In a Eureka! moment, Edison soon realized that sound recording and playback didn’t need a telephone at all. As his chief assistant, Charles Batchelor, later recalled:
One night after supper Mr. Edison suddenly remarked, “You know, Batch, I believe if we put a point on the center of that diaphragm and talked to it whilst we pulled waxed paper under it so that it could indent it, it would give us back talking when we pulled the paper through the second time”. The brilliance of the suggestion did not at first strike any of us—it was so obvious that everyone said “Why of course, it must!” I said, “We’ll try it mighty quick!” and we went to work. In a matter of an hour or so we all got together to make a trial. We fixed the instrument onto a table and I put in a strip of paper and adjusted the needle point until it just pressed lightly on the paper. Mr. Edison sat down and, putting his mouth to the mouthpiece, delivered one of our favorite stereotyped sentences used in experimenting on the telephone “Mary had a little lamb” whilst I pulled the paper through. We looked at the strip and noticed the irregular marks, then we put it in again and I pulled it through as nearly at the same speed as I had pulled it in the first place and we got “ary ad elll am” – something that was not fine talking, but the shape of it was there. We all let out a yell of satisfaction and shook hands all round.
By August Edison was using the word “phonograph” to describe his invention. Lab notes show him and his men considering a wide range of recording techniques – some of which were built, most of which remained ideas. Late in November sketches were drawn for a phonograph that recorded on tinfoil wrapped around a revolving cylinder. Made by mechanic John Kruesi, this iconic machine was not the first phonograph – but it was the first to be shown outside the lab.
On December 7th Edison, Batchelor, and Edward Johnson paid an unannounced call to the editors of Scientific American in New York to demonstrate the new phonograph:
Mr. Thomas A. Edison recently came into this office, placed a little machine on our desk, turned a crank, and the machine inquired as to our health, asked how we liked the phonograph, informed us that it was very well, and bid us a cordial good night. These remarks were not only perfectly audible to ourselves, but to a dozen or more persons gathered around, and they were produced by the aid of no other mechanism than the simple little contrivance explained and illustrated below.
For Edison, sound recording and sound playback were two necessary aspects of the same endeavor. The practical requirements of telegraph companies to time-shift and speed-shift electronic communications led him to a means of recording voices and sounds for all time, just as Scott de Martinville did. Edison, however, made the recordings to be played back by machine, not read by eye as Scott intended.