American composer Maryanne Amacher created what she called “Third Ear Music”, often making use of psychoacoustical effects such as second order beats and otoacoustic emissions, tiny sounds that our ears emit in response to – as well as in the absence of – sound. Second order beats play with our perception of phase, which is often used during localization to tell which direction a sound is coming from. In this case it’s possible to misinterpret the tonal information of a mistuned interval as spatial information. The nature of this particular piece is such that, when played loudly in a room, it can appear to sound like a rotating tone inside each listener’s head. Some people find that their perception of the melodic sequence actually changes by tilting their heads from side to side and moving around the room.

Amacher said of these compositions: “when played at the right sound level, which is quite high and exciting, the tones in this music will cause your ears to act as neurophonic instruments that emit sounds that will seem to be issuing directly from your head … (my audiences) discover they are producing a tonal dimension of the music which interacts melodically, rhythmically, and spatially with the tones in the room. Tones ‘dance’ in the immediate space of their body, around them like a sonic wrap, cascade inside ears, and out to space in front of their eyes … Do not be alarmed! Your ears are not behaving strange[ly] or being damaged! … these virtual tones are a natural and very real physical aspect of auditory perception, similar to the fusing of two images resulting in a third three dimensional image in binocular perception …”

Note: This illusion does not work over headphones.

A flute hocket performed by two Kuna men from Panama. According to the liner notes: “two players on homemade alto flutes improvise polyphony together. Each flute has several contiguous tones of breathy quality. The flutes are [usually] a fourth or fifth apart…” Around 40 seconds in one of the men adds his voice into the mix too. Recorded by Prof. Clyde Keeler

Hollerin’ is a form of yodeling, one of the oldest forms of long-distance communication. Often using the natural acoustics or resonances of a space to reinforce and carry the message, yodelers are also adept at transitioning between vocal registers, focusing on and emphasizing the break that occurs at the boundary rather than smoothing it. This creates a unique timbre in the middle of a rapid leap from low to high that further disrupts our ability to track the melody and maintain auditory streams, often resulting in a kind of pseudo-polyphony.

This 1975 performance is from the still yearly contest in Spivey’s Corner, North Carolina.

Recording: Old-timey Holler/Ditty by Leonard Emmanuel, Hollerin’, Rounder Records, 1995

This one demands headphones! Here’s yet another variation of the same Amadinda xylophone music I’ve posted previously, except that it’s now panned so that the physical distance between the parts is increased, causing a new perception of the melody and rhythm. Researcher Albert S. Bregman explains: “the piece starts with the two parts interleaved and playing to both ears. Then the first part moves to the left ear, and the second to the right, leading to the separate perception of the two parts with their own isochronous rhythms and the loss of the high and low emergent parts with their irregular rhythms.”

Akazehe Par Une Jeune Fille, from Burundi.  

In a yodeling technique similar to the hockets I posted before, this young girl uses both of her vocal registers, rapidly alternating between high and low notes to create the impression of many notes at once. Often referred to as virtual or pseudo polyphony, this illusion occurs when rapidly occurring notes are far enough apart in pitch to create separate perceptual streams. Because we are tracking several different streams happening in rapid succession we then have limited attention to give to the end of the first note of any given pair. This skews our perception of when the note may have in fact ended, allowing for the belief that both notes are happening within the same time frame.

In this example, the streaming effect appears to be further influenced by the changes in timbre that her voice undergoes when she switches registers. Similarly, streaming factors like variations in timbre and the physical distance between multiple singers can also create pseudo polyphony in a traditional hocket.  

Recording: Musique du Burundi, Ocora Records, 1968.

In this next version of the same Amadinda xylophone song I’ve been posting about, the way that we perceive the melody is drastically altered by the placement of each part in a different pitch range. According to Bregman “the lower part begins alone. Then it is joined by the higher part.  Because the two are an octave apart, their individual isochronous rhythms continue to be heard, and the emergent high and low irregular rhythms are lost.”  Because the distance between parts is sufficient for us to separate them out into two different streams, they remain distinct and rhythmically uniform, never merging to create a more complex combined rhythm.  You can hear the original example of how we can perceptually merge the parts into one stream to make a new rhythmic pattern here.

Copyright Albert S. Bregman.

These Wahgi and Chimbu melodies played on “Spirit Flutes” from New Guinea are part of an initiation ceremony.  Performed by four men, this hocket appears to very gradually gain speed as it progresses, contributing to its dizzying affect.

According to (Rev. ) Louis J. Luzbetak, S. V .D., Ph. D, who recorded it: ”Flutes #1 and #2 are in medium low register, about a half-step apart, and at first they alternate. Later they are joined by another flute a minor third below flute #2, and the final flute is a fifth below this. In one passage the two highest flutes alternate, but with the medium-range flute coming in between.”

Recording: Primitive Music Of The World, Selected and Edited by Henry Cowell, Ethnic Folkways Library FE 4581