The Speech-to-Song Illusion

Chapter 10 begins with the author’s discovery that a phrase she had enunciated—“Sometimes behave so strangely”—when presented repeatedly, came to be heard as sung rather than spoken. This illusion is presented as a sound example. It shows that speech can be perceptually transformed into song without altering the sounds in any way, or by adding any musical context, but simply by repeating a phrase several times over. The speech-to-song illusion, as Deutsch named it, has no obvious explanation in terms of current scientific thinking about the neural underpinnings of speech and music. Many researchers believe that speech and music are each analyzed in independent modules, based on their physical characteristics. This view was supported by studies of stroke patients, some of whom lost their power of speech while their musical abilities remained intact, whereas others lost aspects of musical ability while their speech remained normal. In contrast, philosophers and composers throughout the ages have argued that a continuum extends from ordinary speech at one end to song at the other, with emotional and heavily intoned speech in between. Some recent brain-scanning studies have supported the idea that speech and song are subserved by the same circuitry, while others have shown that song involves more brain regions than speech. Evidence for these different views are currently being debated, but the exact explanation for the speech-to-song illusion remains a mystery.

Strange Loops and Circular Tones

Chapter 4 explores a class of musical illusions and paradoxes that involve the circular dimension of pitch. Pitch can be described in terms of two dimensions. The first is called pitch height, which can be experienced by sweeping one’s hand from left to right up a piano keyboard. The second is a circular dimension known as pitch class, which defines the position of a tone within the octave. Circularity effects in music are analogous to many of the visual works of M. C. Escher, and have been employed in music for hundreds of years. However, with the advent of computer music, striking pitch circularities became possible. The circular scales invented by Roger Shepard (based on Shepard tones) and circular glides invented by Jean-Claude Risset are explored. These remarkable illusions of ever-increasing (or ever-decreasing) pitch are presented as sound examples. They have powerful emotional effects, and their influence in musical compositions, such as the soundtracks and sound design of The Dark Knight and Dunkirk, is described. A new way of producing pitch circularity, which was invented by the author, is also discussed. This new algorithm can be used with natural instrument sounds, and so opens the door to new compositional opportunities.

Introduction

THIS BOOK IS about the auditory system—its remarkable capabilities, its quirkishness, and its surprising failures, particularly as revealed in our perception of music and speech. Over the last few years, scientists have made dramatic advances in understanding the nature of this system. These have involved research in many disciplines, including psychology, psychoacoustics, neuroscience, music theory, physics, engineering, computer science, and linguistics. I hope to convey to you some of the discoveries and conclusions that have resulted from these findings, from the involvement of different brain regions in analyzing the various characteristics of sound, to the principles by which we organize the patterns of sound we hear and represent them in memory. I will be focusing on my own research, and hope to communicate to you the excitement of carrying out explorations in this field, much of which is still uncharted territory, and where there are so many discoveries still to be made....

Conclusion

The Conclusion draws together the findings concerning music and speech that are explored in the book, and the insights derived from these findings. Much of the book is concerned with illusions. Some of the illusions reflect huge differences between people in how they perceive simple musical patterns. These differences suggest variations in brain organization and environmental exposure. Another way in which these illusions shed light on hearing involves illusory conjunctions. These lead to the conclusion that, normally, the process of analyzing sound includes the operation of specialized modules that each analyze a particular attribute, and that we combine the outputs of these modules to obtain an integrated percept. This process usually leads us to perceive sounds correctly, but it breaks down under certain circumstances, producing illusions. Further threads that run through the book involve relationships between music and speech; the importance of unconscious inference, or “top-down processing” on our perception of sound; and extremes of musical ability, which are shown to be the products of both innate and environmental factors. It is also shown that earworms and musical hallucinations highlight the vital role played by the inner workings of our musical minds in determining what we hear. The extraordinary phenomena explored in this book lead us to conclude that the hearing mechanism did not arise as a coherent, integrated whole, but rather developed as a set of different, though interconnected, mechanisms. From another perspective, they elucidate factors involved in listening to music in everyday life.

Hallucinations of Music and Speech

Chapter 9 discusses the rare phenomenon of musical hallucinations. For some they are unwanted, persistent, and dramatically intrusive. Others hear phantom music that is sophisticated, beautiful, and sometimes original. People often describe their hallucinated music in terms of “playlists” composed of music in many different genres, from which fragments seem randomly selected. One such playlist might include folk songs, religious hymns, Christmas carols, patriotic songs, and children’s songs. The music often sounds as though played on a scratched or broken record, or on a tape constantly being rewound. Musical hallucinations are most likely to be experienced by elderly people with hearing loss, but young people with normal hearing, including excellent musicians, also experience them. Some may be caused by an unusually large amount of brain activation, particularly in the temporal lobe. People who have been isolated for long periods may also experience hallucinations, including of music. Hallucinations of speech are also described and discussed. Reports of musical hallucinations show that the different attributes of music can be retrieved or lost independently. A hallucinated piece might be heard in the wrong tempo or loudness, or as played by an unknown instrument. Famous musicians who hallucinated music include Robert Schumann, Bedřich Smetana, and Sviatislav Richter.

The Tritone Paradox

Chapter 5 explores the tritone paradox—a musical illusion that was discovered by the author. Its basic pattern consists of two computer-generated tones that are related by a half-octave (i.e., a tritone). These tones are well defined in pitch class (note name) but ambiguous in pitch height. When one of these tone pairs is played in succession, some people hear an ascending pattern, yet other people hear a descending one. Indeed, a group of people will disagree completely among themselves as to whether such a pair of tones is moving up or down in pitch. Furthermore, any one person hears one of these tone pairs as ascending or descending depending on their note names (such as C–F♯, or G♯–D). How people hear the tritone paradox varies with the geographic location in which they grew up—and so with their native language or dialect. Native English-speaking Californians hear this pattern differently from natives of the south of England. People who are natives of Vietnam hear the pattern quite differently from native English-speaking Californians. The tritone paradox shows, therefore, that the way we perceive music is related to our language, and generally reveals strong effects of our memories and expectations on how we hear music. It also has important implications for absolute pitch (or “perfect pitch”)—the rare ability to name a musical note that is presented in isolation. People make orderly judgments of the tritone paradox, even though they cannot name the notes that they are judging, so they must have an implicit form of absolute pitch.

Speech and Music Intertwined

Chapter 11 explores relationships between speech and music. The history of thought about these relationships is reviewed. The importance of prosody in speech—musical qualities such as variations in pitch, tempo, timing, loudness, and sound quality—is discussed. There follow reviews of the emotional response of infants to the musical qualities of their mothers’ speech, and how such qualities help children acquire language. Further studies are discussed indicating that musical training aids children in processing the prosodic qualities of speech. Other studies show an influence of language on music perception. The tritone paradox, discussed in Chapter 5, shows that how people hear a pattern of tones can vary with the language or dialect to which they were exposed in childhood. Also, as discussed in Chapter 6, speakers of tone language, such as Mandarin, Cantonese, and Vietnamese, have a far higher prevalence of absolute pitch in music than do speakers of non-tone languages such as English. Other work has shown an influence of language on the perception of timing in music perception, and on musical composition. Yet music and language generally differ in their physical characteristics and functions. Whereas speech serves primarily to inform the listener about the world, music modulates feelings and emotions. Last, the question of how music and speech evolved is discussed, and it is argued that they may both have their origins in a vocal generative system called musical protolanguage.

Catchy Music and Earworms

Chapter 8 begins with “stuck tunes” or “earworms,” a malady that strikes most people at times: A tune or other musical fragment bores deep into our heads and replays itself over and over, sometimes for hours, days, or even weeks. It is argued that the present epidemic of earworms is partly due to background music being heard everywhere, and to people listening to music fairly continuously over their radios, televisions, iPods, and other devices. This constant exposure to music could sensitize our music processing systems so strongly that they tend to fire spontaneously. Several famous musicians have publically decried the ubiquity of background music, arguing that it debases our musical experience. In the past, all music was sung or played live, and in certain venues such as churches, concert and dance halls, or at special events such as birthday and wedding celebrations. Another source of earworms may be the frequent repetition of phrases within a song, a device that is now extremely common in popular music. The popularity of a song based on sales, radio play, and online streaming increases with the amount of repetition within the song. The tendency for music to get stuck in our heads makes it ideal for radio and TV advertisements—a catchy tune can turn into an earworm, and carry the name of the product along with it.

Phantom Words

Chapter 7 discusses the fact that when listening to speech, the words and phrases we hear are strongly influenced by our knowledge, beliefs, and expectations. We therefore often mishear words and phrases, and are subject to compelling illusions. One illusion that was created by the author is called phantom words, and examples of this illusion are presented. A sequence is played consisting of two words, or a single word composed of two syllables, and these are repeated many times. The same sequence is presented via two stereo loudspeakers, but offset in time so that when the first sound is coming from the speaker on the left, the second sound is coming from the speaker on the right, and vice versa. Because the signals from the two speakers are mixed in the air, we can create in our minds many different combinations of sounds. Many people initially hear a jumble of meaningless sounds, but distinct words and phrases later emerge, followed by new words and phrases. Nonsense words and musical sounds sometimes appear mixed in with meaningful words. The words and phrases often appear to be spoken in strange or “foreign” accents—presumably listeners are perceptually organizing the sounds into words and phrases that are meaningful to them, even though they appear distorted in consequence. These phantom words are similar to those reported by people who believe they come from the spirit world. Also discussed is the technique of recording spoken phrases backward and playing them forward, leading to the claim that satanic messages can be heard from these recordings.

The Mystery of Absolute Pitch

Chapter 6. discusses absolute pitch (or “perfect pitch”)—the rare ability to name a musical note in the absence of a reference note. It is argued that acquiring absolute pitch requires exposure to certain environmental influences during a critical period early in life. This ability is associated with early musical training—and the earlier the onset of training the stronger the association. The author and her coworkers have found at music conservatories and universities in the United States and China that the earlier students had begun taking music lessons, the greater the probability that they possessed absolute pitch. We also found that the prevalence of absolute pitch is much higher among people who speak a tone language—in which the meaning of a word changes depending on the pitch or pitches in which it is spoken. It is therefore argued that when babies learn to speak a tone language, they automatically associate pitches with words, and so develop absolute pitch for the words they hear. Therefore when they begin taking music lessons, their brain circuitry for absolute pitch is already in place. Speakers of non-tone languages are therefore at a disadvantage compared with tone-language speakers for acquiring absolute pitch. Further work by the author and colleagues also point to a genetic factor in acquiring absolute pitch. Also discussed are the neurological correlates of absolute pitch, and its presence in some autistic savants, and in people who are blind. It also considers the decline of absolute pitch with aging, and distortions in absolute pitch judgment under certain medications.