Musical relativity

Musical relativity

Here’s a neat idea for a concert that’s going to blow a few minds if it ever takes to the stage.

A combination of three or more notes played together is called a chord. We know that certain musical chords sound happy while others sound sad (although nobody knows why). The mood of a piece of music then depends on the combination of chords being played. More than a few weighty tomes have been written about the way one chord can be transformed into another and the effect this has on the mood of the music.

But Kaca Bradonjic, a physicist at Boston University, says that musicians appear to have ignored one of the fundamental ways of changing the pitch of a note: the Doppler shift. He points out that it ought to be possible for an observer moving at a specific velocity to hear a sad sounding note as a happy one and vice versa.

Which means that the mood of a piece of music depends on the relativeĀ  velocities of the audience and performers.

He calculates for example that to hear a C major chord as a C minor, the listener would need to be travelling at about 43 miles per hour, directly away from the source. That’s a fair speed. And the accelerations necessary to vary this effect from one note to another during a concert would make this one helluva roller coaster ride.

Talking of which, a (very quiet) roller coaster might be the perfect venue forĀ  the first concert of this type.

Ref: arxiv.org/abs/0807.2493: Relativity of musical mood

7 Responses to “Musical relativity”

  1. Whether a particular chord of scale sounds sad is very much culturally dependent. Just listen to the funeral music of the South Seas, which to Western ears can sound very, very jolly. Whereas emo goths will always perceive any music as misery inducing regardless of tempo, pitch, timbre, or any other factors, Dopplerized or not.

  2. Alex Spencer says:

    Wouldn’t you only want to doppler shift the E note in the Cmaj chord to an Eb to get a C minor? If you shift all three notes lower, you would just get a Bmaj. Am I wrong? Is there some part of physics I am unfamiliar with that causes different frequencies to doppler shift by different amounts?

  3. To KFC,
    There is a bit of a misunderstanding in your text: “musicians appear to have ignored one of the fundamental ways of changing the pitch of a note: the Doppler shift. ” I am sure that most of musicians are aware of the Doppler shift of a single tone. I am pretty certain that lot of software for electronic music making have Doppler effects you can use. What I was aiming at was a change of how a combination of tones sounds when you jump into a different reference frame.
    Thanks for the post!

    Dear David,
    Yes, that’s right. Where I come from there is music that sounds really vibrant, fast, but if you listen to the lyrics, it goes something like “she left me, and it is the end of the world, and i will drink the whole bar tonight.” But that is not the point. All I wanted to say is that whatever the mood of a song is when listened to at rest, it will be changed when you start moving.

    Dear Alex,

    You are right. If you read the paper, you will see that it exactly like that. But you could choose to play around a bit and see how things sound when you shift the other tones. As far as I know, there is no frequency dependence of the Doppler effect.

  4. PS: I am not a guy. :)

  5. Kent Quirk says:

    The Doppler effect changes pitch proportionally — all pitches will change by the same fraction. So if you start with an A major chord, for example (A C# E), and you fly your band in room-temperature air at 146 MPH towards the observer, the chord will change to a C Major chord (the 440 Hz A will change to a 423 Hz C, etc). So basically, Doppler effect can transpose a tune but it can’t change it from major to minor.

  6. Kent Quirk says:

    whoops, that was 523 Hz C — sorry for the typo

  7. Kaca Bradonjic says:

    RE: Kent Quirk

    What you say is true if all three tones are coming from a same source/speaker. What I considered is three tones that are coming from three different sources and can be approximated by plane waves which are propagating in three perpendicular directions, call them x, y, and z. If the observer is moving in the x direction only, then only the sound propagating in x direction gets Doppler shifted. The other two stay unchanged, so you can, in fact, go from a major to a minor. You can also find the velocity at which the whole tune gets transposed.