Do we really sing as well as we all think we do in the shower? Exactly how complex is Mel Taylor’s drumming in Wipeout? How we hear things is important not just for the field of music research, but also for the fields of psychology, neurology, and physics. There is a lot more to how we perceive sound than sound waves just hitting our ears. PLOS ONE recently published two research articles exploring music perception. One article focuses on how perceiving a sound as higher or lower in pitch—the frequency of a musical note relative to other notes—than another sound is influenced by different instruments and the listener’s musical training. The other explores rhythm, including musicians’ perception of rhythmic complexity.
Pitch is the frequency of a sound, commonly described using the words high or low. The quality of tone, or timbre, of an instrument, on the other hand, is less easy to define. Tone quality is often described using words like warm, bright, sharp, and rich, and can cover several frequencies. In the study presented in “The Effect of Instrumental Timbre on Interval Discrimination,” psychology researchers designed an experiment to determine if it is more difficult to perceive differences in musical pitch when played by different instruments. They also tested whether musicians are better at discriminating pitch than non-musicians (you can test yourself with this similar version) to see if musical training changes how people perceive pitch and tone.
The researchers compared the tones of different instruments, using flute, piano, and voice, along with pure tones, or independent frequencies not coming from any instrument. As you can see from the figure above, each instrument has a different frequency range, the pure tone being the most localized or uniformly “colored.” Study participants were given two choices, each choice with two pitches, and decided which set of pitches they thought were the most different from each other; sometimes they compared different instruments or tone qualities and sometimes, the same.
The researchers compared the participants’ answers and found that changes in tone quality influenced which set of pitches participants thought were the most different from each other. Evaluation of the different timbres showed that musicians were the most accurate at defining the pitch interval with pure tones, despite their training in generally instrumental tones. Non-musicians seemed to be the most accurate with both pure and piano tones, though the researchers noted this might be less reliable because non-musicians had a tendency to choose instrumental tones in general. Interestingly, both groups were faster at the pitch discrimination task when pure tones were used and musicians were better at the task than non-musicians. Everyone chose pitch intervals more accurately as the differences between the pitches became larger and more obvious.
Another group of researchers tested how we perceive syncopation, defined as rhythmic complexity, in their research presented in “Syncopation and the Score” by performing an experiment playing different rhythms to musicians. They asked musicians to rank the degree of complexity of each rhythm.
The study was limited, with only ten participants, but in general, the rhythm patterns thought to be the most complex on paper were also perceived as the most complex when the participants listened to them. However, playing the same patterns in a different order sometimes caused listeners to think they were hearing something more or less syncopated. The authors suggest that a rhythm pattern’s perceived complexity depends upon the rhythm patterns played before and after it.
Both research studies highlight the intersection of music and music perception. We don’t need to be musicians to know that music can play tricks on our ears. It may be that some of us are less susceptible than others to these tricks, but even trained musicians can be fooled. Look here for more research on music perception.
Zarate JM, Ritson CR, Poeppel D (2013) The Effect of Instrumental Timbre on Interval Discrimination. PLoS ONE 8(9): e75410. doi:10.1371/journal.pone.0075410
Song C, Simpson AJR, Harte CA, Pearce MT, Sandler MB (2013) Syncopation and the Score. PLoS ONE 8(9): e74692. doi:10.1371/journal.pone.0074692
Image: Spectrograms of four tones – Figure 1A from Zarate JM, Ritson CR, Poeppel D (2013) The Effect of Instrumental Timbre on Interval Discrimination. PLoS ONE 8(9): e75410. doi:10.1371/journal.pone.0075410