Art by Daniel Špaček.
This episode was written and produced by Andrew Anderson.
In the 1960s, stereo sound revolutionized the music industry. But it turns out, a pioneering engineer named Alan Blumlein had actually invented stereo a full three decades earlier. Due to tragic events in World War II, his innovations were forgotten for decades. In this episode, we worked with OnePlus to tell the story of how audio has evolved from mono, to stereo, to quadraphonic, to surround sound and beyond. Today, we even have immersive, three-dimensional systems that can simulate 128 speakers using just two. Featuring Alan Blumlein’s son Simon Blumlein, and sound engineer Robin Reumers from the Abbey Road Institute.
MUSIC FEATURED IN THIS EPISODE
Original music by Wesley Slover.
Fixation by Pendulum Theory
The Glow Worm by Victor Orchestra
Stompin’ Jazz Night by Golden Age Radio
Hotsie Totsie Lotsie by Martin Landstrom
Vintage Dream by Mathilda June
The Heart Knows by Luella Gren
Descent by Peter Sandberg
All We Need by Rotem Sivan
Toccata and Fugue in D Minor by Leopold Stokowski
All Night by Edwin Violet
Don’t Stop by King Rose
Arcaders by Ben Elson
Belladonna Blue by Rotem Sivan
Flurry by Roary
Watermark High by Traveller
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View Transcript ▶︎
[sfx: airplane, 1940s bomber]
[music in]
It's June 1942, at the height of World War 2. A British bomber plane is flying over the south of England. But it isn't carrying weapons. Instead, it's carrying a new radar system.
Several engineers are on board to test it, including a man named Alan Blumlein. Alan is just 38 years old, but he's already worked on tons of innovative projects. And if this radar works, it could help the Allies win the war.
But this is one project that Alan won't complete. Because, an hour after take off, the plane crashes. There are no survivors.
Prime Minister Winston Churchill says that Alan's death must be kept a secret. The enemy can not know that Britain has lost one of its best engineers. Because of Churchill's orders, Alan's name is quickly forgotten`. And so are many of his inventions, including another revolutionary idea: stereo sound.
[music crossfade into stereo moment, then Dallas verb out]
You're listening to Twenty Thousand Hertz.
[music in]
Alan Blumlein was born in London, in 1903.
Simon Blumlein: He went to different schools…
That's Simon Blumlein, Alan's son.
Simon Blumlein: …Some of which were quite free schools and didn't press him to do work.
Despite not being pushed at school, Alan quickly showed his engineering talent.
Simon Blumlein: The doorbell on the house broke…
[sfx: door bell warbling brokenly]
Simon Blumlein: …and he repaired it at the age of seven.
[sfx: door bell]
For his handiwork, young Alan issued an invoice… to his father.
Simon Blumlein: He got a lot of engineering encouragement from his father.
Although he was brilliant with numbers and mechanical things, Alan sometimes struggled with words. Here's his wife Doreen in a BBC interview from the ‘90s.
Doreen Blumlein: He couldn't read properly at all until he was about 12. So I said, "But you couldn't read properly till you were 12". He said, "No, but I knew a lot of quadratic equations."
[music out]
That talent for equations took him to college, where he managed to finish his degree in just two years. After that, Alan started to work at a company called Standard Telephones and Cables. His first invention for them involved fixing an issue with telephone lines.
Simon Blumlein: At the time, there could be crosstalk between the different circuits.
Crosstalk is where you could hear someone else's conversation when you were using the phone.
[sfx: phone calls getting mixed]
Simon Blumlein: So he had to find a solution... and with clever engineering he got rid of a lot of it.
[sfx: phone calls become clear]
But some of his greatest inventions were in the field of music.
[music in: Golden Age Radio - Stompin’ Jazz Night]
In the late 1920s he joined the Columbia Graphophone Company, which later became EMI Records. His first task was to create an electronic recording system.
Simon Blumlein: The electrical recording system was the thing of the moment because before that, everybody had to speak into horns.
These were big megaphones that captured sound.
Simon Blumlein: And it's very difficult getting a whole orchestra in front of a horn.
At the time, EMI didn't have their own electronic recording system. Instead, they used one created by RCA in the United States. That meant that they had to pay royalties on every single vinyl record they made. So to get around this, they reached out to Alan.
Simon Blumlein: And he went into the interview, and he heard all what was required and said, "Yes, I can do it, but I don't think you'll be able to afford my salary."
So EMI doubled their offer, and within two months, Alan had created a new electronic recording system.
Simon Blumlein: And therefore they managed to stop paying the royalties.
[music out]
Alan's electronic recording system was impressive. But his next invention would change music forever.
[sfx: cinema sounds / 1930s movie playing]
Simon Blumlein: He took my mother one day to the cinema, and he said to her, "Do you notice that as this person talking on the screen moves across the screen, the sound stays in one position?”
That observation gave him an idea, and soon enough he applied for a patent.
Simon Blumlein: Binaural is what he called it, but we nowadays call it stereo.
Alan's idea was revolutionary. It allowed vinyl records, movies and even radio to have two soundtracks rather than one.
In movies, Alan's system recorded sound information on either side of the film strip - one side for the left audio channel, and one side for the right. This created a more immersive experience. Suddenly, a character’s voice and footsteps could follow them as they moved across the screen.
Here's a recording of Alan testing his stereo system in his office at EMI.
Alan Blumlein: Now I'm walking across pretty quickly, going over to the other side. Coming over quite steadily on full binaural. Coming right over steadily on full binaural. Trot, do you get that alright? Good, thank you.
[sfx: needle drop]
[music in]
For vinyl records, Alan’s system cut different patterns on each side of the groove. Then, one side of the needle picked up the left channel, while the other side picked up the right.
Now, each instrument could have its own space, creating much more clarity and depth. To this day, vinyl records work the exact same way.
[music out]
Then came the biggest test yet: recording a full orchestra at EMI's brand-new Abbey Road Studio. For that, the London Philharmonic Orchestra performed Mozart's Jupiter Symphony.
[clip: Jupiter symphony]
The improvement over mono was obvious. Here’s the mono version they recorded at the same time.
[track switches to mono version]
And now back to stereo.
[track switches back to stereo version]
His fellow engineers were amazed, but the managers at EMI didn't recognize the potential. The company was selling tons of mono records - so why should they switch to stereo?
On the other hand, there was a new medium that they did believe in: television. And the BBC had just contracted them to make Britain's first television system. So, as their top engineer, EMI put Alan in charge of taking them into the televised age.
[music in]
To test this new equipment, he had a television installed in his home. Then, he filmed himself from his office, and broadcast the images to his family. Here's his wife Doreen.
Doreen Blumlein: He would ring me up and say, "Hold the telephone darling, and look in the set. Now tell me what you could see." This was early television. And I'd say, "Well, I can see the smoke from your pipe". Of course, he was never departed from his pipe, except in bed.
After three years of research and testing, Alan and his colleagues were ready. The first ever BBC television broadcast took place in late 1936.
Announcer: Hello everyone. This is Elizabeth Cowell introducing a BBC television service program from Alexander Palace. This afternoon, our program includes a Marionette show, newsreel, and ballet.
Alan also invented the wiring used for outdoor broadcasts. That got its first trial during the coronation of King George the VI in 1937.
Announcer: I can see the King and Queen smiling at their subjects as they go by. The Queen is smiling at us now. And they, they look incredible! They look like something out of a picture book!
Although he was only one year old at the time, Alan’s son Simon got to watch on television at home.
Simon Blumlein: I don't remember a thing about it, but I was there. There was only three thousand sets in 1937, and they reckoned 10,000 people saw it.
[music out]
Alan kept working on television technology until the beginning of World War II in 1939. But the BBC worried that the television transmitter could help aid the enemy’s navigation systems. So as the war started, they shut down all television broadcasts.
[sfx: TV switched off sound]
Not long after that, Alan joined the government's H2S radar project. That was a kind of radar that could be carried onboard bomber planes.
Simon Blumlein: Churchill demanded 200 sets of this H2S system. It can see through clouds and the bomber could get a picture of the site that they want to bomb.
The project was top secret, and not even his family knew what he was working on. Here's Doreen Blumlein.
Doreen Blumlein: And when the war started, he said to me, "I shall not be telling you anything of what I'm doing, because I'm not allowed to speak about it.”
Alan and his team spent eighteen months developing the H2S radar system. By June 1942, they were ready for a test flight. Alan decided that he wanted to take part.
[sfx: plane taking off]
[music in]
Simon Blumlein: In the end, 11 people got on board and my father was able to see the results.
The radar system worked just as they hoped. All of that hard work had paid off. But sadly…
Simon Blumlein: On the way back a starboard engine caught fire. The pilot was desperately looking for somewhere to land the plane before the fire got worse.
The pilot tried to land the plane safely, but ended up crashing.
Simon Blumlein: All 11 on board were killed.
Simon was only six at the time, but he still remembers that day.
Simon Blumlein: Our house was at the end of the row. I walked on into the house, and there was mama crying her eyes out.
Since the H2S project was top secret, Winston Churchill ordered that no one should be able to know about the crash. As a result, only Alan's family heard about his death. And that had a huge impact on his legacy.
Simon Blumlein: Because nothing had been written, there was no recognition in the country.
[music out]
Alan's tragic death meant that he never got the recognition he deserved during his lifetime. But over the next couple of decades, people slowly started to rediscover his inventions - including stereo.
In the early sixties, a full thirty years after Alan had developed it, stereo sound was finally installed at Abbey Road studios. And that system found its way into the hands of an exciting young band.
[clip: The Beatles on Ed Sullivan]
That's coming up, after the break.
[clip out]
~MIDROLL~
The first sound recording machine that could also play back that sound was invented in 1877 by Thomas Edison. In his first recording, Edison chose to read a nursery rhyme.
Thomas Edison: Mary had a little lamb, its fleece was white as snow, and everywhere that Mary went that lamb was sure to go.
That recording was in mono, which meant it only had a single channel of audio.
Robin Reumers: Mono was actually how everything started.
[music in]
Robin Reumers: My name is Robin Rumors. I'm mainly a mixing engineer based out of Miami.
Robin has worked with all kinds of artists, including Spanish pop icon Alejandro Sanz, Canadian singer-songwriter Alessia Cara, as well as Queen’s legendary guitarist Brian May.
Robin Reumers: He was so nice about everything. And that of course was a highlight because who isn't a fan of him?
Robin also lectures at the Abbey Road Institute, a school for music producers. There, he teaches students how to work with all kinds of audio - including mono recordings.
Robin Reumers: So with mono you have a single speaker, which is your main sound source. All of the sounds like for example, your guitars, your bass, your drums, your vocals would all come from a single speaker, so you would put everything in one place and you would balance the instruments.
Robin Reumers: When you're mixing in mono, it really forces you to focus on making sure that yeah, your mix translates and does what it needs to.
The downside is that everything can start to sound crowded. It's like all the instruments are trying to squeeze through one door, and they end up getting squashed.
[music out]
Alan Blumlein's stereo system was one solution to the problem. But he wasn't the only person trying alternatives. Walt Disney also thought that audio could be recorded on multiple channels. So, for the 1940 film Fantasia, his team created a system they called Fantasound.
[music in]
First, Disney engineers placed 30 microphones around the orchestra. The audio was then recorded onto tape machines in the basement below.
[sfx: tape machine]
The result was a recording that could have up to seven channels.
[music up, then out]
Fantasound was incredible. But it was also expensive, complicated and unreliable. As a result, Fantasound was only featured at special screenings of Fantasia, and it wasn’t used on any other Disney films.
[music in]
Then in the late 1950s, engineers at Bell Labs invented their own stereo system. Or at least, they thought they had. They didn’t realize that Alan Blumlein had invented stereo almost thirty years before.
Here's one of Alan’s colleagues recalling how he broke the news to the team at Bell Labs.
Colleague: And then he turned around and said, "Well that’s impossible, because you see we've got patents on all this." I then laid Blumlein's patent on the table, and there was dead silence for about five minutes. They didn't even know it existed!
But once stereo caught on, it started to be installed in studios. One of the first to have it was Abbey Road in London. And one of the first bands to record with it was a little group called… The Beatles.
[music out]
[clip: The Beatles - Please Please Me]
The Beatles were known for being innovative in the studio. But this new technology confused them at first.
Robin Reumers: The Beatles for example, they initially thought, "Okay, we have two speakers, so let's put the drums in one and put the bass in the other and then the vocals in the left one again.”
As a result, the original stereo mixes of their albums sound a little strange to modern ears. For example, here's what their song Girl originally sounded like in stereo. The vocals are panned all the way to the right, and the instruments all the way to the left.
[clip: The Beatles - Girl]
Robin Reumers: There's a very famous story about Paul McCartney. He said that basically they had taken their mix that they had done where they had half of the instruments in one speaker and half in the other, and he went to a party [sfx] and they basically had two speakers, and one was in one room and one was in the other.
Robin Reumers: And when he was listening to the music, he was like, "Hey, half of my instruments are gone." At which point he realized maybe it's not such a good idea to do like the hard pan, because you don’t know how people are going to end up consuming the music.
Perhaps this approach isn't surprising, because mixing in stereo is different from mixing in mono.
Robin Reumers: When you open it up to stereo, of course you have to think about more possibilities. You have to think, "Oh, now I have left, right. What do I place where?" And it makes you think differently about the mix process.
But over time, people learned to make the most of stereo.
Robin Reumers: In general, people like to use the full stereo spectrum. Most of the key lead instruments are typically panned in the middle, like vocal, kick, snare, bass. And then all the other instruments, like a piano can be on the left, guitar on the right, or vice versa.
[music in]
Robin Reumers: So for example, you might start a song off that is very intimate and very narrow, as in most things in the middle.
[music: song gets bigger]
Robin Reumers: But then when the chorus hits, you want to open up the sound and that's when you can have more instruments panned left or right.
[music: add chorus parts panned]
Robin Reumers: So you start having a lot more possibilities.
[music out]
Eventually, The Beatles remixed their early stereo albums in a more conventional way. Here's that recording of Girl in its original stereo format.
[clip: The Beatles - Girl]
And here’s the remix.
[clip: The Beatles - Girl (Remixed)]
[music out]
[sfx: announcement]
Now, from here on out, all of the examples we play will be in stereo. That’s because even if you’re listening on a multi-speaker system, the MP3 format used by podcasts only has two channels of audio. Womp womp.
[sfx: announcement out]
But stereo wasn’t the end of the story. Because in the early 70s came quadraphonic, which featured four sound channels.
[sfx: four chords, left, left center, right center, right]
You have rear left, front left, front right, and rear right.
Early artists to use quadraphonic included the Byrds, with Byrdmaniax.
[clip - The Byrds - I Wanna Grow Up to Be a Politician]
Pink Floyd also released a quadraphonic version of Dark Side of the Moon.
[clip: Pink Floyd - Any Colour You Like]
But quadraphonic albums were expensive to make, and were designed to be played on a special turntable. If you played them on a normal deck…
…They would often skip.
[skipping VO + music, then music out]
So quadraphonic was eventually left behind, and music stayed in stereo. But in the late 70s, the movie industry was experimenting with something new: SURROUND SOUND!
[music in]
Robin Reumers: That was really like a major push and all the movie theaters converted to having surround sound.
Although different studios used different systems, they were all based on having five audio channels.
Robin Reumers: It would be left…
[sfx: ping]
Robin Reumers: …center …
[sfx: ping]
Robin Reumers: …right…
[sfx: ping]
Robin Reumers: …left surround…
[sfx: ping]
Robin Reumers: …which would be, you know, in the back…
[sfx: ping]
Robin Reumers: …and then right surround.
[sfx: ping]
Robin Reumers: So those are your five main channels.
Robin Reumers: That kind of change in the infrastructure would come from the movie theater owners. And it was a consensus of like, "we wanna up the quality of the experience".
[music out]
One of the first directors to use surround sound was Francis Ford Coppola, with Apocalypse Now. Coppola wanted his epic war story to have an equally epic soundtrack.
[clip: Apocalypse Now]
There was only one problem - when he started the project in 1974, movie theaters didn't have surround sound yet. But Coppola had a solution for that. Here's the film’s sound designer Walter Murch, in a 2006 documentary.
Walter Murch: At a certain point, Francis decided that the film was only gonna be shown in one theater. Uh, it was gonna be a specially built, constructed theater that would be erected in the geographic center of the United States, somewhere in Kansas. And it would just show this film only, and the film would run for 10 years. And it would be a fantastic cinematic experience, sort of like going to Mount Rushmore.
In the end, the film took so long to make that movie theaters caught up with Coppola’s ideas. In 1979, Apocalypse Now was released in surround sound, across the United States. The following year, it won the Oscar for Best Sound.
[music in]
Audiences loved the immersive feel of surround sound, and before long it was everywhere. Almost every blockbuster in the 1980s used it, from The Empire Strikes Back…
Darth Vader: Your destiny lies with me, Skywalker..
…to Batman.
The Joker: Batman. Can you hear me? Just the two of us, mano a mano.
While surround sound was impressive, it's actually not what we associate with movie theaters today.
Robin Reumers: The next evolution that really caught on was 5.1.
Five point one came along in the early 90s, and it had six channels of audio rather than five. That might not sound like a big change, but that point one makes a huge difference.
Robin Reumers: The way it works is that the first number is your main speakers. And then the point 1 is your LFE, your Low Frequency Effects.
That extra channel of bass audio created the punch that we now associate with the big cinematic experience.
Robin Reumers: Jurassic Park was the first movie where they incorporated that low frequency channel to basically have the rumble of the dinosaurs and make that come through in cinema.
[music out into Jurassic Park clip]
This low frequency channel also made it possible to create our old friend, the King of modern movie trailers, The Booj.
[sfx: booj]
As well as its cousin, the Bwah.
[sfx: bwah]
But there were still more channels of audio to come. We had speakers all around us, but not above us. That all changed in the early 2010s.
[music in]
Robin Reumers: The next evolution is object-based audio, where you’re no longer limited by a set number of speakers. But instead what you do is you create objects.
Robin Reumers: So every object is a mono audio file, and it comes with location information. So for example, I can have a lead vocal and it has x, y, and Z coordinates.
Robin Reumers: So you can place it in the 3D sphere and that then gets translated by the renderer to the amount of speakers that your system has. So if you have a speaker system that has 128 speakers, it will render it differently than when you have a speaker system that has 5.1 speakers. So you have a lot more creative freedom when it comes to mixing.
[music out]
There are several object-based audio systems, but the most famous one is Dolby Atmos. And the first movie to use it, was Pixar's Brave in 2012.
[clip: Brave]
Now, every blockbuster has some version of it.
[music in]
Until recently, it seemed like immersive audio was everywhere… except in music.
Robin Reumers: When it comes to music, there wasn't really that like global consensus of, "Oh, we should all consume music in 5.1 or 7.1," or whatever the format is. I think most people were happy with what they had in stereo.
Part of the problem was that spatial audio was expensive. You had to have multiple speakers, as well as a device that could render that audio. But then, headphones were developed that recreated the effect of having 128 speakers… with just two.
The science behind this is a little complicated, but let's demonstrate. Normally with old fashioned stereo headphones, a sound arrives in your left ear...
[sfx: left]
But with spatial audio headphones, the sound arrives in your left ear and then - with a slight delay - in your right ear.
[sfx: left with delay right]
This simulates how we actually hear audio in real life. By using this, and a few other clever tricks, spatial audio headphones manage to overcome having just two channels.
[music out]
As a result, musicians are now experimenting with object-based spatial audio. For example, Disney star Olivia Rodrigo's 2021 album Sour was mixed in spatial audio.
[clip: Olivia Rodrigo - Good 4 U]
And Hollywood legend Hans Zimmer remixed his track Lost but Won, from the movie Rush, for this new technology.
[clip: Hans Zimmer - Lost But Won]
[music in]
Spatial audio has already revolutionized the way we experience movies, games and now music. But we’ve only scratched the surface of what’s possible.
Robin Reumers: I think the possibilities are just endless. I told you earlier on the story of Paul McCartney when they were just discovering stereo and panning something left and panning something right. I feel like when it comes to immersive audio, we're still kind of at that stage, like everybody's still exploring, experimenting, finding out what works, what doesn't work. So I think it's a very exciting time to be doing this.
But none of it would be possible without that first step taken by Alan Blumlein back in the 1930s
Simon Blumlein: He said that he was so lucky to be where he was because there were so many things that needed solving. He just loved getting the solution.
And for Simon, restoring his dad's legacy has been his lifelong project.
Simon Blumlein: It's been my aim in life, ever since I lost my father. Looking back on his life, I know my father so well now.
In 2017, something totally unexpected happened. The Recording Academy of the United States gave Alan a posthumous Grammy for his work. And Simon was there to collect the prize.
Simon Blumlein: It was a wonderful occasion. And I held it up and said, "I've waited 75 years for this recognition of my father. Daddy, this is yours."
[sfx: cheering]
Simon Blumlein: It was the shortest speech and it got the biggest applause.
[music + sfx out]
[music in]
Twenty Thousand Hertz is produced out of the sound design studios of Defacto Sound. Find out more at Defacto Sound dot com.
This episode was written and produced by Andrew Anderson. It was story edited by Casey Emmerling, with help from Grace East. It was sound designed and mixed by Colin DeVarney and Brandon Pratt.
Thanks to OnePlus for making this episode possible, and thanks to our guests, Simon Blumlein, and Robin Ruemers.
I’m Dallas Taylor. Thanks for listening.
[music out]
