The Tritone and the Ambiguity of Pitch

Over the end of the year holidays, Trudie and I became obsessed with the Irving Berlin song, I’ve Got my Love to Keep Me Warm. We were humming it around the house, dancing to it. Then I got caught up in the unusual harmonics of the line “I can weather the storm”. The tune goes quite minor and slightly dissonant until the line emerges from the “storm”. How did Irving do that?

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The four syllables “weather the storm” move up in stacked minor thirds (which accounts for the minor), then within that a pair of tritones for the dissonance. The last note on “storm” is the key tone for the song, so all that minor dissonance gets to resolve on a positive note. Wow! That is a beautiful marriage of words and music, brought to you, in part, by the augmented fourth/diminished fifth/half octave – better known as the tritone.

The tritone is an amazingly powerful interval. It was labeled “Diabolis in Musica” and shunned in music of the church in the 18th Century. The tritone can invoke a strong unpleasant reaction from the listener due to its harmonic dissonance and associations with the devil. Happily, modern music composers have rescued the tritone from the narrow and incomplete sense bestowed by the church. Leonard Bernstein used the tritone throughout the score of West Side Story, which helped to frame the longing, sadness, and excitement that are also a part of the feel of the tritone. George Harrison used the tritone in many of his songs, which is why they always stood out from the more bouncy, sweet Lennon-McCartney tunes. The tritone leant an air of exotic mysticism to his music.

The tritone also figures prominently in a perceptual paradox of psychoacoustics. Upon hearing two musical tones played in succession, most people can accurately determine which pitch is higher and thus whether the interval goes up or down. When all the intervals are tritones, listeners fall into two camps: the fundamental tone hearers can accurately determine the intervalic movement, while overtone hearers are less accurate in making this determination. There is a test for this on-line, so I took it and got 11/12. A fundamental tone hearer am I!! Interestingly, the interval I was incorrect on was one where I heard the fundamental go one direction and the overtones suggest the opposite direction. I realized I heard it, but got confused as to which one was which and picked the wrong answer. Here is a wonderful example of the profound teaching in mistakes – that moment of confusion occurred because I had a realization of how much more there was to hear. I heard that the fundamental tone and the harmonics are connected but also seperate and distinct. Once again I am bowled over by the profundity of awakening to a larger perception of things!

Then a mystery of pitch ambiguity threw itself at me. I was playing some chord progressions on a particular synth instrument in Ableton, and, when I moved from a DFAC chord down to CEGB, the tonal center seemed to move up! I kept playing the chords and watching my hands to confirm that “Yep, my hands are moving down the keyboard” and listening as the tone rose each time. It was messing with my mind. Then I listened through my monitors and heard the same thing. Here is a recording of this instrument playing these two chords in order to illustrate the phenomenon. Keep in mind as you listen that the chord progression is a higher chord to a lower chord.

I think this could be an example of overtones obscuring the fundamental tone, which would contribute to pitch ambiguity. I sent the recording to Ableton and asked about how the instrument was modeled and shaped. I am quite curious about the possibility of some kind of tritone relation in the harmonics of this particular instrument. Or does the second chord pull out higher Cs that brighten the sound and create a sense of rising tone?

I will keep you posted as the mystery unfolds!

4 thoughts on “The Tritone and the Ambiguity of Pitch

  1. I agree with you, but I also think as an alto, you are used to listening to the inside voices and those pitches go up. Most people would hear the chord as a whole where I think the inside notes sound more pronounced for us.

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    • Yes, Robin, I do think singing alto shaped my hearing “into” chords. Interestingly, Diana Deutsch at UC-San Diego has been researching the way the tritone paradox is influenced by language and dialect as well. Very interesting stuff. Thanks for reading and commenting!

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