Week 4

This week you will learn about the concepts of pulse and entrainment in the theory track.

The terminology track will focus on the motion of perceiver’s, people experiencing music.

Finally, in the methods track we will take a closer look at motion capture systems that can be used outside of the lab, what we call mobile mocap. Remember to use the dictionary.

4.3 The Feeling of Pulse and the Entrainment Process

A fundamental property of music is its ability to structure time. Elements like recurring sounds and accentuations express an organization of the musical events into periods of a certain length that can be measured according to a tempo as divisions of clock time (beats per minute). In popular music this tempo is generally steady (isochronous) and expressed most clearly by the drums, with recurring bass drum and snare drum sounds usually playing a central role. In classical music there is more common with small tempo variations. This is called rubato.

To what extent do rhythmic groupings of music have connections to the human body? The connection is most apparent in how rhythmic groupings can be expressed through movements like head nodding (or head banging), foot or finger tapping or upper body bouncing. The ability to perform such movements in synchrony with music is widespread and cross-cultural, and for most dancers and musicians it is often essential for their ability to perform their tasks.

Moreover, it is a very human ability � not observed performed by species closely related to us. In Coldplay�s music video for the song �Adventure Of A Lifetime� (2015) they have chimpanzees that move in synchrony to music. These animals are of course fake. No animal have been successfully trained to perform anything like this (except a cockatoo called Snowball that you can find on several YouTube-videos bouncing back and forth in synchrony to the beat).

Entrainment is a term that describes a process where one rhythm adopts the period and phase of another. If you place two pendulum clocks on the same surface and start them out of phase they will eventually end up in synchrony according to how well the surface transfers oscillations. This term is also used on behavioural processes where we, for example, coordinate our actions with others, and fits well on the human ability to synchronize with the rhythm in music (see Clayton et al. 2005).

Musicologist Mari Riess Jones has done many studies of rhythm in music. She uses the term entrainment to describe how our attention (or attentional energy) may oscillate according to a musical rhythm (Jones 2004) with flexibility to variations and tempo shifts. This process supports dynamic system theories of cognition and from this body of work she has adopted the term attractors or attractor points. When two oscillations interact there are points in their trajectories that are especially significant for how they align (Kelso 1995).

Events in music that are vital for an entrainment process can likewise be named attractors, since they can cause a type of bodily oscillation. Her claim supports the existence of neural oscillations; processes of repeated neural activity that facilitate the performance of cyclic operations (see also Stern 2004:80).

Neural oscillations are also probably active in entrainment processes when repeated movements to musical rhythms are performed. Daniel Schneck and Dorita Berger point to the correspondences between rhythmic pulse in music and muscle activation:

Rhythmic pulsation embodies a consistent symmetrical balance of energy output, of fall and rebound� of tension and relaxation. Rhythmic vibration in music involves the same steady stream of force-rest-force-rest, of systematic strong and weak impulses, of alternating flexion (contraction), release (relaxation), and extension as in the case for paired and coupled muscular behavior. (Schneck and Berger 2006:139, emphasis in original).

The musical pulse transfers a rhythmic vibration of oscillating energy that can coordinate muscular behaviour.

Via dynamic system theories of cognition where bodily actions are seen as highly significant (see Thelen and Smith 1994 and Kelso 1995), a framework for the entrainment process may be outlined; certain repeated sounds or accentuations in the music function as attractors that form an oscillating energy that coordinate (entrain) neural oscillations of muscular behaviour.

In dance music productions a steady stream of bass drum sounds is often used to make the pulse unambiguously present. These are typical attractors. The rhythmic energy pounds steadily and the listener may respond with various types of corporeal up-and-down movements.

A hi-hat sound (or a similar high frequency sound) is often added in between the bass drum sounds (on the off-beats) doubling the number of attractors, marking out an opposite point in the rhythmic energy and the trajectory of an up-and-down movement (ex: Gloria Gaynor: �I Will Survive�, Cher: �Believe�).

Moreover, a snare drum sound may replace or supplement every second bass drum sound causing certain variations to the rhythmic energy and thus to the corporeal movements.

There are not many rhythmic patterns that have a clearer connection between sounds and rhythmic pulse than the pattern described above, and it is, probably for this reason, used in numerous dance music tracks. More generally in music attractors do not occur that frequently, and they can be formed by different musical elements and be more difficult to identify.

What is considered the pulse may also be ambiguously communicated and there are many cases of more complex and compound rhythms. The rhythmic feel � often expressed through a repeating rhythmic groove � is an essentially vital element in much music. It gives the audience the opportunity to move along to the music in meaningful ways and it forms fundamental aspects of mood and feeling.

Many times an unambiguous pulse may be communicated throughout the whole song, but how it is done always varies along the way. Which instruments that are present and how they participate in this action can shape a kind of corporeal journey from start to end. Of course other elements are active in shaping this journey (harmonies, melody, sound, lyrics, etc.), but my argument here is that the main pulse is more than just divisions of clock time. The feeling of pulse plays a significant role in how music can express a diversity of mood and emotional content.

References:

4.4 Pulse and Music Culture

Although our ability to entrain to an external rhythm might be innate, the perception of an underlying reference structure in music�for example, the underlying pulse�is also highly dependent on the music culture. Our perception is determined by our previous experience, and by repeated regularities in our environment.

Music culture can be defined as what arises when multiple people share a repertoire of musical concepts and practices (Baily 1985, Blacking 1995). For example, did Hannon and Trehub (2005) find culture-specific musical biases between adults from Bulgaria and Macedonia (who are exposed to music with a non-isochronous pulse) and adults from North America (who are mainly exposed to music with an isochronous pulse). This suggests that pulse perception also depends on one�s familiarity with the specific music culture.

Sometimes the underlying reference structures such as the pulse are not necessarily represented by the actual sonic events. For example, in the beginning of �Stir It Up� by Bob Marley, the guitar riff is played between the pulse beats. However, a perceiver familiar with reggae would immediately recognize the underlying pulse despite (or because of) the off-beat guitar riff. In other words, the underlying reference structure is sometimes indicated by style-specific recurring rhythmic patterns that do not follow the underlying pulse.

So how can the underlying pulse be identified if it is not present in the sounding music? As previously mentioned, the pulse level in music is often externalized through body motions. Agawu (2003) describes how the underlying reference structure in many West and Central African dances is indicated by typical rhythms that do not follow the underlying pulse, which is only visible in the corresponding dance (Agawu 2003:73). In a study of Brazilian drum patterns, Kubik (1990) explains that, since the percussionists� �inner pulsation� was often not present in the sound, one had to find it in the body motion of the musicians and dancers.

In music styles like traditional Scandinavian folk dance the cue is not in a specific sonic rhythm but in a more complex implied pattern. Blom (2006) points out that the underlying pulse in certain traditional Scandinavian dance music genres consists of non-isochronous sequences, and that this underlying structure should be understood in relation to the dancers� vertical motion of their center of gravity and the musicians� foot stamping.

We have seen that in some music styles, the underlying pulse does not coincide with sonic events, but is derived from a rhythm pattern typical for the style of music. In other styles of music, like some Scandinavian dance music genres, the cue is not in a specific sonic rhythm but in a more complex pattern. Either way, however, we find the same mechanisms of cultural learning.

References:

4.5 An Analysis of a Ritardando

Ritardando is a musical term (from Italian) for a deceleration in tempo. In the following a ritardando in a song is analysed in accordance to the theory presented in this course.

The song “Take Me Out” by Franz Ferdinand (from 2004) has an electric guitar intro that actually sets a pulse with a particularly fast tempo (286 bpm). The repeated guitar tones are identical, which is a typical characteristic of musical elements that mark downbeats. However, this tempo is so fast that most bodily up-and-down movements (head nodding, foot tapping) become very tedious or difficult to perform. Thus, a bodily interpretation of what is the main pulse will more likely be half the tempo (143 bpm) even from the very start.

This interpretation is confirmed when the verse starts. A hi-hat with accentuations on every second guitar entry marks the downbeats of this slower tempo. Half way through the verse (0:20) a bass drum is added also marking the downbeats, making this slower pulse even more definite. How the pulse is interpreted from the start of the song may not be crucial to the experience, but the energy that this part expresses gives a kind of aggressive mood to the opening of the song.

The most interesting section of Take Me Out in relation to entrainment and pulse is the ritardando from 0:50 till 0:56; when the tempo during two bars slows down from the initial 143 bpm to 104 bpm.

Throughout this section a bass guitar doubles the initial energetic guitar theme while bass drum sounds clearly mark the downbeats. The ritardando is audible from 0:50, but a slight deceleration has already taken the tempo down from 143 to 140 bpm. When it truly starts, it has a smooth descend to 123 bpm during the first bar, continuing down to 104 during the last.

To establish the new tempo and confirm that the ritardando now has ended, four downbeats are marked with all instruments. In Kronman and Sundberg�s (1987) study of musical ritardando they argue for connections to natural decelerations in physical human movement. Their belief is that we recognize how the ritardando develops from patterns in our human experience of slowing down the speed of bodily movements.

In “Take Me Out” the diminutive early ritardando probably prepares the listener unconsciously of what will come. Then the smooth ritardando develops according to a natural deceleration of a physical movement. Since a ritardando may signal a continuing path to a full stop, the music has to clearly confirm that the ritardando now has ended and a new tempo is established.

After the slower tempo is established through four bars of clear energetic downbeat markings, a new guitar theme is introduced. A this point the hi-hat is moved to the off-beats. They can be experienced as attractors marking an opposite position of the downbeats in a bodily up-and-down movement.

In popular music and especially dance music, an off-beat hi-hat (or similar high frequency sounds) very often corresponds to the peak position of an up-and-down movement. Both the guitar theme and the following vocals also have their highest note entry on the off-beat followed by a descending interval. Are such structural positions coincidental or do the alternation of low and high sounds and matching ascending and descending melodic lines fortify experiences of up and down when moving to a rhythmic pulse? ( - this will be further discussed in week 6)

References:

4.9 Introduction to Perceiver Movements

In the previous videos in the terminology track we have looked at different types of music-related body movement in performers. This week we will look more at the perceivers, that is, people experiencing music.

Before we get started with the video, it may be useful to recall that we use the term perceiver to focus on the multimodal approach to the experience of music. While we often talk about “listening” to music in our daily life, this usually implies a truly multimodal experience. Few people really mean that they only listen to the sound of the music, even though this is of course also possible. But as we have looked at earlier, listening to the sound is only one part of the experience. The visual element is also crucial, and other senses too even the taste music. Yes, everyone that has played a wind instrument will know that music can taste something. Ask your clarinet playing friend!

But what types of movements can be found in perceivers? Generally, we may find all the same type of movements in perceivers as in performers, including sound-producing. A main difference, though, is that perceivers are usually not the main focal point in a musical context. That is the role of the performers. Still, we have found that studying the body movements of perceivers can be very interesting. After all, a person’s behaviour may reveal a lot about his or hers cognitive state and experiences.

4.12 Mobile Motion Capture

Sometimes, it is relevant to capture the movement of performers or perceivers outside of a laboratory setting. This can be for research purposes � studying how performers or perceivers move in a real concert; or it can be an interactive part of the performance, tracking the movement of a performer or perceiver to influence visual displays or the musical sound. This article presents some of the technologies you will see in the next video step.

The most precise way of recording motion is in a dedicated motion capture (mocap) laboratory with optical infrared cameras and reflective markers. However, there are several reasons why we might want to use other types of motion capture systems to studying music-related motion:

  • cutting edge camera-based mocap technologies are expensive
  • setting up a camera-based system in a “real” setting (such as a concert hall) is visually distracting and might be disturbing to the performer
  • lighting conditions are often less than ideal when measuring people’s body motion in a “real” situation (as opposed to in a mocap lab).

Inertial measurement units (IMUs)

Inertial sensors operate on the physical principle of inertia:

  • Accelerometers measure acceleration
  • Gyroscopes measure the amount of rotation of the sensor.
  • Magnetometers measure the orientation in relation to the earth’s magnetic field (as a compass)

Magnetometers are strictly speaking based on magnetic sensing, not inertial, but are often included in what is called inertial measurement units (IMU). An IMU is inside most modern smart phones and tablets, and makes it possible to estimate orientation and acceleration.

The Xsens Suit

At the University of Oslo we have an Xsens suit, which consists of 17 IMUs in combination with a kinematic model of the human body. The kinematic model restricts the possible position of each of the IMUs, and thus facilitates calculating the position of each sensor based on the acceleration and rotation data provided by the sensors.

The Xsens suit makes it possible to record motion in any location. It can also be used in real time and the motion data can be used as an interactive element of a music performance. Here is an example of the Xsens suit used in performance. In the video, the performer is controlling a number of synthesizers with his movements. The data is fed to a program called Ableton Live, where certain parts of the music are pre-composed some parts are controlled by the performer (e.g. triggering new sections and selecting between different chords). We will look more closely at such interactive music technologies in the methods track in week 6.

Suggested literature

Up next

Week 5