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Category: Music
Tunes without composers: music naturally evolves on DarwinTunes
The tunes embedded above weren’t written by a composer, but fashioned through natural selection. They are the offspring of DarwinTunes, a program which creates bursts of noise that gradually evolve based on the preferences of thousands of human listeners. After hundreds of generations, tracks that are boring and grating soon morph into tunes that are really quite rhythmic and pleasant (even if they won’t be topping charts any time soon).
DarwinTunes is the brainchild of Robert MacCallum and Armand Leroi from Imperial College London. “We suspected that musical styles evolve through Darwinian natural selection,” says MacCallum. “They are copied and modified from artist to artist and generation to generation, with popular styles more likely to be copied as they get more exposure. “ The duo created DarwinTunes to see if music could actually evolve in this way.
The DarwinTunes tracks are all 8-second-long loops, each encoded by a ‘digital genome’ – a program that determines which notes are used, where they’re placed, the instruments, the tempo, and so on. The genomes of two parent loops can shuffle together in random ways to produce daughter loops, which also develop small random mutations. This mimics the way in which living things mate and mutate. It also mimics the way in which composers merge musical styles together, while inventing new motifs.
The experiment began with 100 randomly generated loops. On the DarwinTunes website, listeners could listen to these and rate them on a five-point scale, from “I can’t stand it” to “I love it”. Every time 20 loops were rated, the top 10 pair off, mate with each other to produce two daughters, and die. At any time, there are only 100 loops in the total population.
To date the loops have been evolving for 3,060 generations, and over 50,000 of them have been born. By taking loops from DarwinTunes’ entire history and asking volunteers to rate them, MacCallum and Leroi showed that they became more appealing with time. For example, they were more likely to contain chords found in Western music and they contained more complex rhythms. “We hoped for slightly more “advanced” music, but were very happy with the results,” says MacCallum.
This upward rise in appeal only lasted for 500 or 600 generations. After that, the loops hit a plateau and apparently stopped evolving. MacCallum and Leroi think that this is because the loops become so complex that their intertwining melodies and rhythms don’t merge very well. The act of mating, rather than combining the best of both parents, ends up splitting up elements that work well together.
Alternatively, it may be that as the loops become well adapted to the tastes of their listeners, it becomes harder to change them without messing something up – they become trapped in an adaptive peak, unable to reach a new peak without first crossing into a valley. Both of these processes have their counterparts in the world of real genetics. MacCallum and Leroi argue that this might explain why many old musical styles tend to be very conservative, changing little over thousands of years.
DarwinTunes is the latest in a line of digital evolution programs, where computer code copies itself, mutates, evolves and adapts. For example, in The Blind Watchmaker, Richard Dawkins describes a programme of the same name that can evolve complex shapes from initially simple collections of lines. These programs never fully reflect the reality of evolution, but they allow scientists to ask basic questions about evolution in a controlled way. They can set up controlled experiments, repeat them, replay evolution from specific points, and analyse how specifically their artificial creations have changed. It’s incredibly hard (but not impossible) to do that with actual living things.
But Michael Scott Cuthbert, who works on computer-aided musical analysis at MIT, is sceptical that the approach tells us anything about the evolution of music. “They have shown that people can sense a glimmer of the things they like about music even when most of it consists of sounds they hate,” he says. “But it doesn’t give any information about why music sounded differently in the past, why people like different things today, or how music might evolve in the future.”
“Suppose you randomly threw car parts into piles and asked people to rate those they’d most like to buy,” he says. “Then you took parts from the highest-rated heaps, and rearranged them into new heaps. People might hate all of them at first, but they’d probably rate the ones with four tires or a trunk in the back or a steering wheel in the drivers’ seat higher than the rest. Do that long enough and I wouldn’t be surprised that you’d eventually get something that looked like a 2011 Honda Civic. But that doesn’t mean that that’s how a car is made.”
MacCallum and Leroi acknowledge that real music changes in a more complex way than DarwinTunes currently captures. Composers write music with their own intentions, while listeners choose music based not just on what it sounds like, but on whether other people like it too. DarwinTunes could be changed to include these dynamics – volunteers could combine the loops themselves, and listeners could see earlier ratings.
“The big question for me is can we bring the quality up a level where you don’t have to be curious about the science to take part?” says MacCallum. “We can do that if we had millions of users, and segregated them based on musical genre preferences. It’s a chicken and egg problem though!”
Reference: MacCallum, Mauch, Burt & Leroi. 2012. Evolution of music by public choice. PNAS http://dx.doi.org/10.1073/pnas.1203182109
Image by Pedro Sanchez
More on music:
- Violinists can’t tell the difference between Stradivarius violins and new ones
- Treating tinnitus with an individually tailored piece of music
- 35,000-year-old German flutes display excellent kraftwerk
- Alex the parrot and Snowball the cockatoo show that birds can dance
- Ballet postures have become more extreme over time
- How Kenny Rogers and Frank Sinatra could help stroke patients
- Why music sounds right – the hidden tones in our own speech
Violinists can’t tell the difference between Stradivarius violins and new ones
Antique Italian violins, such as those crafted by Antonio Stradivari or Giuseppe Guarneri “del Gesu”, can fetch millions of dollars. Many violinists truly believe that these instruments are better than newly made violins, and several scientists have tried to work out why. Some suspected at the unusually dense wood, harvested from Alpine spruces that grew during an Ice Age. Others pointed the finger at the varnish, or the chemicals that Stradivari used to treat the wood.
But Claudia Fritz (a scientist who studies instrument acoustics) and Joseph Curtin (a violin-maker) may have discovered the real secret to a Stradivarius’s sound: nothing at all.
The duo asked professional violinists to play new violins, and old ones by Stradivari and Guarneri. They couldn’t tell the difference between the two groups. One of the new violins even emerged as the most commonly preferred instrument.
Treating tinnitus with an individually tailored piece of music
Many of us have just spent the Christmas season with a persistent and irritating ringing noise in our ears. But now that the relatives have gone home for the year, it’s worth remembering that a large proportion of the population suffers from a more persistent ringing sensation – tinnitus. It happens in the absence of noise, it’s one of the most common symptoms of hearing disorders, and it’s loud enough to affect the quality of life of around 1-3% of the population.
There have been many suggested treatments but none of them have become firmly established and most simply try to help people manage or cope with their symptom. Now, Hidehiko Okamoto from Westfalian Wilhelms University has developed a simple, cheap and enjoyable way of reducing the severity of the ringing sound. The treatment has showed some promise in early trials and even better, it is personally tailored to individual patients.
The method is simple. Find out the main frequency of the ringing sound that the patient hears – this becomes the target. Ask the patient to select their favourite piece of music and digitally cut out the frequencies one octave on either side of this target. Get the patient to listen to this “notched” piece of music every day. Lather, rinse and repeat for a year.
Okamoto tried this technique in a small double-blind trial of 23 people, eight of whom were randomly selected to receive the right treatment. Another eight listened to a piece of music that had a random set of frequencies cut out of it, while seven were just monitored. The treatment seemed to work. After a year, the treatment group felt that their ringing sensation was around 30% quieter, while the other two groups showed no improvements.
35,000-year-old German flutes display excellent kraftwerk
Thirty-five thousands years before the likes of Kraftwerk, Nena and Rammstein, the lands of Germany were resounding to a very different sort of musical sound – tunes emanating from flutes made of bird bones and ivory. These thin tubes have recently been uncovered by Nicholas Conard from the University of Tubingen and they’re some of the oldest musical instruments ever discovered.
The ancient flutes hail from the Hohle Fels Cave in Germany’s Ach Valley, a veritable treasure trove of prehistoric finds that have also yielded the oldest known figurative art. The flutes were found less than a metre away. Together, these finds show that Europeans had a rich artistic and musical culture as far back as the Upper Palaeolithic period, some 35,000 years ago.
Conard unearthed the new finds last year, including several flutes of ivory and bone. One of these was found in 12 separate pieces, but once they were recovered and united, the insturment proved to be remarkably complete. It was so beautifully preserved that we can even work out its source – its maker fashioned it from the arm bone of a griffon vulture, a large species with long bones that make for good wind instruments.
The flute is just 8mm in diameter and has five finger holes along its 22cm length. Around each hole, there are up to four precisely carved notches, which Conard thinks were measurement markers that told the tool-maker where to chip an opening. Two deep, V-shaped notches were also carved into one end, which was presumably where its maker blew into to make sweet, prehistoric music.
Alex the parrot and Snowball the cockatoo show that birds can dance
Snowball, the sulphur-crested cockatoo, is an internet superstar. He’s known for his penchant for grooving to music, notably Everybody by the Backstreet Boys. As the music plays, Snowball bobs his head and taps his feet in perfect time with it. If it speeds up or slows down, his rhythm does too. He is one of two parrots that are leading a dance dance revolution, by showing that the human behaviour of moving in time to music (even really, really bad music) is one that’s shared by other animals.
People who’ve attended parties at scientific events may question the ability of humans to move to a beat, but it’s a fairly universal skill and one that many people thought was unique to our species. After all, domesticated animals like dogs and cats don’t do it, and they spend their time with humans and have been exposed to our music for thousands of years. Other animals may produce periodic sounds or perform complex dances, but sensing and moving in time to complex rhythms is a different matter.
Snowball and his feathered friend Alex (the late, famous African grey parrot) could change all of that. Aniruddh Patel from San Diego’s Neurosciences Institute found evidence of Snowball’s excellent rhythm under laboratory conditions. Before Alex’s recent death, Adena Schachner from Harvard University (working with Alex’s keeper, the renowned parrot psychologist Irene Pepperberg) found that he could also match Snowball’s bopping.
Both groups of researchers believe that the parrots’ dancing skills depend on a talent for “vocal learning” – the ability to mimic the sounds of other individuals. To do this, animals need to have excellent coordination between their sense of hearing and their motor functions. Indeed, after searching YouTube for videos of dancing animals, Schachner only found evidence of moving to beats (a talent known as “entrainment”) among 15 species that practice vocal learning – 14 parrots and the Asian elephant.
Ballet postures have become more extreme over time
Classical ballet is one of the more conservative of art forms. Dancers express emotion and character through the same vocabulary of postures that was originally set in 1760, and often with entire choreographies that have been handed down for centuries.
But even amid this rigorous cascade of tradition, there is room for change. Over the years, successive generations of ballet dancers have subtly tinkered with positions that are ostensibly fixed and limited by the physical constraints of a dancer’s body. The only changes ought to be a result of the dancers’ varying abilities. But that’s not the case – over the last 60 years, the position of a dancer’s has become increasingly vertical, with the moving leg in particular being lifted ever higher.
Elena Daprati from the University of Rome thinks that these tweaks have been driven by social pressures from audiences. When she reduced pictures of dancers to stick-figure drawings, she found that even people who have never seen a ballet prefer the postures of modern dancers to those of dancers 60 years ago. The results suggest that art can change very gradually because of constant interactions between performers and their audiences.
Almost more importantly, they show that the usually unquantifiable world of artistic expression can be studied with a scientific lens. In this case, the formal nature of classical ballet gave Daprati a rare opportunity to do so. Body postures could be objectively analysed, movements are standardised enough to allow for easy comparisons, and most of all, performances have been carefully archived for decades. That provided Daprati’s group with more than enough raw material for studying the evolution of ballet postures over time.
How Kenny Rogers and Frank Sinatra could help stroke patients
We’re used to thinking of neglect as a lack of appropriate care, but to a neuroscientist, it has a very different meaning. “Spatial neglect” is a neurological condition caused by damage to one half of the brain (usually the right), where patients find it difficult to pay attention to one half of their visual space (usually the left).
This bias can affect their mental images too. If neglect patients are asked to draw clocks, many only include the numbers from 12 to 6, while some shunt all the numbers to the right side. When two famous neglect patients were asked to describe a familiar square in Milan, the city they grew up in, the landmarks they reported shifted depending on where they pictured themselves standing in the square. They would only report buildings to the right of their imagined position – swap the location and new buildings would suddenly come into mental view.
Patients tend to be particularly unaware of things on the left if other objects on the right are vying for their attention – this phenomenon, where only one of two simultaneously presented objects is seen, is called “visual extinction“.
Neglect is clearly a fascinating condition but also a debilitating and underappreciated one. It affects up to 60% of patients who suffer strokes on the right side of their brain, and it can hamper recovery and deny patients their independence. As such, there are plenty of researchers interested in finding ways of improving its symptoms. David Soto from Imperial College London is one of them, and he has discovered a deceptively simple way of helping neglect patients to regain their lost awareness – listen to their favourite music.
Soto was encouraged by a recent study, which found that stroke victims showed greater improvements in both memory and attention when they tuned into music than when they listened to audiobooks or worked in silence. And other studies have suggested that emotional faces are less likely to fall prey to visual extinction than less compelling images. But Soto wanted to see if the patient’s own emotional state had anything to do with their awareness. Would it be possible to reduce the symptoms of neglect simply by making patients feel happier through the medium of pleasant melodies?
Why music sounds right – the hidden tones in our own speech
Have you ever looked at a piano keyboard and wondered why the notes of an octave were divided up into seven white keys and five black ones? After all, the sounds that lie between one C and another form a continuous range of frequencies. And yet, throughout history and across different cultures, we have consistently divided them into these set of twelve semi-tones.
Now, Deborah Ross and colleagues from DukeUniversity have found the answer. These musical intervals actually reflect the sounds of our own speech, and are hidden in the vowels we use. Musical scales just sound right because they match the frequency ratios that our brains are primed to detect.
When you talk, your larynx produces sound waves which resonate through your throats. The rest of your vocal tract -your lips, tongue, mouth and more – act as a living, flexible organ pipe, that shifts in shape to change the characteristics of these waves.
What eventually escapes from our mouths is a combination of sound waves travelling at different frequencies, some louder than others. The loudest frequencies are called formants, and different vowels have different ‘formant signature’. Our brains use these to distinguish between different vowel sounds.
Female antbirds jam their partners' songs when other females approach
The songs of birds certainly sound beautiful to our ears but listen closely and you’ll hear a world of conflict and subterfuge. Take the Preuvian warbling antbird (Hypocnemis peruviana). Males and females live in pairs and they will defend their territories from other duos by singing beautifully coordinated duets.
Theirs is a most melodious partnership but throw another female into the mix and the harmony breaks down. The duet turns into an acoustic battle – the female tries to jam the song of her partner with her own, so that the notes of his amorous solo fail to reach the ears of the intruder. The male in turn adjusts his song to avoid his mate’s interference.
Joseph Tobias and Nathalie Sneddon uncovered this complicated sonic rivalry by recording 27 pairs of wild warbling antbirds in their natural environment in Peru. Males and females sing different tunes and their duets consist of a regular series of couplets – the male always leads and the female chimes in immediately after. These couplets require split-second timing. If she comes in any earlier, the female interferes with the male’s song.
But she often does. The quicker she responds to his song, the greater the interference, and the more likely the male is to take counter-measures. If he’s being sung over, the male abandons his current son and just begins a new one after the female finishes. In very rare situations, she jams him again, and the cycle continues.
Butterflies scrounge off ants by mimicking the music of queens
Ants are among the most successful of living things. Their nests are well-defended fortresses, coordinated through complex communication systems involving touch and chemical signals. These strongholds are stocked with food and secure from the outside world, so they make a tempting prospect for any burglars that manage to break in.
One species of butterfly – the mountain alcon blue (Maculinea rebeli) – is just one such master felon. Somehow, it manipulates the workers into carrying it inside the nest, feeding it and caring for it. The caterpillar does so little for itself that it packs on 98% of its eventual adult weight in the company of ants. How does it do it?
Partly, the caterpillar secretes chemicals that imitate those found on ant larvae, and it mimics their actions too. But that can’t be the only explanation for ant workers will actually rescue alcon blue caterpillars over their colony’s genuine larvae. And if food is short, they will even kill their own young to feed the parasitic impostors. In the entire colony, only one individual is treated with as much respect as the caterpillars – the queen.
Now, Francesca Barbero from the University of Torino has found out how the alcon blues manage to get the royal treatment – they “sing” in the style of queens, producing uncanny cover versions using instruments built into their bodies.
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