This Is Your Brain on Music: The Science of a Human Obsession

Chapter 1 provides a basic introduction to music theory for readers without prior knowledge of the subject. Levitin notes that the many diverse genres of music can all be distinguished from nonmusical sounds because they are “organized” and share certain features and characteristics. He defines and explains terms and concepts that he uses throughout the remainder of the book, though with the caveat that even within the field of music theory, no universal consensus exists on the precise definition or characteristics of many of these terms. To avoid ambiguity or miscommunications, Levitin clearly outlines his own understanding and usage of each key word.

He first identifies separable features of music that can be altered and studied independent of any other elements, including pitch, rhythm, tempo, contour, timbre, loudness, and reverberation. Combining and building on these fundamental concepts produces other important characteristics such as meter, key, melody, and harmony. Levitin elaborates on many of these terms throughout this chapter and the rest of the book.

Loudness is a purely psychological construct that relates to the amplitude of a note (or “tone” in scientific parlance) and how much energy an instrument produces when displacing air. Rhythm refers to the length of notes in a sequence, and tempo refers to the overall pace of a piece of music: how fast or slow the regular beats of the music are. Meter is a construction by which the brain groups the beats of a piece of music together using loudness and rhythm as cues. Contour describes the shape of a piece of music, taking into account only whether notes go up or down in pitch, while reverberation refers to what a layperson thinks of as “echo”—how distant a source of music sounds and the perceived acoustic qualities of the surrounding space. Timbre refers to the overall mood of a piece of music and the characteristic sounds of particular voices or instruments.

Melody is the key theme of a piece of music that is central to the variations in a classical piece or sung by a vocalist. It is a purely relational feature, recognizable by the relationship between its components rather than by the innate features of the composite notes in isolation. Harmony refers to a parallel melody or progression of chords that accompanies the main melody of a piece, guiding expectations and forming a consonant background or enhancement to the melody. Key is a hierarchical organization of notes within a musical piece, named for the central tone in the key (for example, C-major or E-minor). The hierarchy is artificial, a consequence of musical tradition guiding expectation.

Pitch is a psychological phenomenon based on how high or low a tone is, dependent on its frequency and relative position on a musical scale. The full range of audible pitches in music are divided into 12 semitones that, in Western music tradition, are labeled either using letters A-G (plus flat or sharp notes in between) or using the do-re-mi system. These 12 notes are repeated because of a perceptual phenomenon in which each time a pitch is halved or doubled, the notes sound remarkably similar. This frequency ratio of 2:1 or 1:2, known as an octave, is the basis of all musical systems around the world. Differing levels of consonance or dissonance characterize intervals within an octave, and the most consonant combinations are the “perfect fourth” and “perfect fifth” (at intervals of five and seven semitones, respectively). Unlike visual inputs like color, pitch is directly mapped in the brain. When the ears hear a particular pitch, specific neurons corresponding to that pitch fire in the brain.

Frequency refers to the vibration of the noise-making element of an instrument (air, string, etc.) and is measured in cycles per second with the unit hertz (Hz). Humans can hear sounds between 20 and 20,000 Hz, and these frequencies are directly mapped from the ear to the brain. The lowest frequency produced when a particular note is played is called that note’s fundamental frequency. Other frequencies are produced as the source vibrates, always at integer multiples of the fundamental frequency. These additional frequencies are called harmonics, and the unique auditory characteristics of different instruments result from the ratio by which energy is distributed between the fundamental frequency of a tone and its harmonics. The ratios differ significantly for different instrument types and less significantly between different instruments of the same type. This is why drums, trumpets, and guitars sound so distinct from each other even when playing the same note, while a trumpet and French horn might sound similar and two trumpets might sound almost identical. Since the 1990s, the mapping of these frequency ratios has enabled the creation of artificial and digital instruments, such as frequency modulation synthesis, that can accurately reproduce the distinctive characteristics of any instrument.