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This is part of a write up im doing for a project regarding music production and this is my Consonance and Dissonance section. Are all points correct here? Many thanks folks!

Consonance and Dissonance

i. Consonance is the harmonic strength/stability of two intervals playing simultaneously such as a chord, while dissonance is the equal opposite. It has lesser harmonic strength and instability that causes tension and desire to be resolved to consonant intervals.

ii. Consonance is produced when two pitches' waves crests and troughs regularly sync up within a time period, such as in an interval or a chord. Dissonance is produced when crest and troughs of two waves have an irregular synchronicity.

iii. There is a system which allows us to organize intervals in ratios from their most consonant to their most dissonant within an octave. These ratios stem from two waves crest/trough activity, as mentioned in the previous point.

iv. The ratio system is not applicable to an entire scale of a key but instead only on a single pitch basis, meaning that when you shift note/pitch of a melody or the root of a chord within a key the latter ratios no longer apply but the ratios have now shifted to the new note in use.

v. In order to make this ratio system function within a key, use the intervals from the ratio structure that are present within the key scale of choice. You can also modulate keys by for example, being in the C Major scale and then exiting the key through making an interval in the C Major scale a transition into a new key.

  • Unison = 1/1 Perfect Consonance (1st note of an octave)
  • Octave = 2/1 Perfect Consonance (13th note of an octave)
  • Perfect Fifth = 3/2 Perfect Consonance (8th note of an octave)
  • Perfect Fourth = 4/3 Dissonant when the bass note (6th note of an octave)
  • Major Sixth = 5/3 Imperfect Consonance (10th note of an octave)
  • Major Third = 5/4 Imperfect Consonance (5th note of an octave)
  • Minor Third = 6/5 Impefect Consonance (4th note of an octave)
  • Minor Seventh = 7/4 Dissonant (11th note of an octave)
  • Tritone = 7/5 Dissonant (7th note of an octave)
  • Minor Sixth = 8/5 Imperfect Consonance (9th note of an octave)
  • Major Second = 9/8 Dissonant (3rd note of an octave)
  • Major Seventh = 11/6 Dissonant (12th note of an octave)
  • Minor Second = 12/11 Dissonant (2nd note of an octave)
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    Unrelated to the definitions in your writeup, you have several spelling mistakes (e.g. "reguarly") and some questionable word choices (mainly your use of "stableness"). Does your project penalize spelling mistakes? – Dekkadeci Jul 12 at 6:56
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    I see misinformation in the first definition. Consonance is not the stability of two or more intervals but 2 notes played simultaneously. 2 notes make an interval and that interval can be judged as consanant or dissonant. When a chord sounds dissonant it can usually be reduced to specific intervals within the chord. So in its most strict form the definition applies to 2 notes being played simultaneously. – ggcg Jul 12 at 18:39
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    You have an incomplete sentence for the Perfect Fourth. – ggcg Jul 12 at 18:42
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    I think you are confusing a note for an interval. An interval of a P4 cannot be a root note of a chord. If you mean a chord built on the 4th degree of the major scale then, for example, a major triad built on the 4th is just as consonant as that built on the 1. – ggcg Jul 12 at 20:44
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    Would you call the destructive interference that can be produced "when two pitches' waves crests and troughs regularly sync up within a time period" (except that the first pitch's crest corresponds to the other pitch's trough and vice versa) consonance per se? I'd call any silence that results neither consonant nor dissonant. – Dekkadeci Jul 13 at 12:50
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As you've said this is for a personal project only, I won't "nit-pick" too much...

Consonance is produced when two or more pitches' waves crests and troughs reguarly sync up within a time period, such as in an interval or a chord. Dissonance is produced when crest and troughs of two or more waves have an irregular synchronicity.

This mostly sounds reasonable, but as I said on one of your other questions, it's only the time domain way of looking at things. The human ear essentially works in the frequency domain.

These ratios stem from two or more waves crest/trough activity, as mentioned in the previous point.

Hmm... it really does seem strange to emphasise this 'crest/trough' thing. This isn't how the human ear works.

The reason that the human ear hears ratios that are close to being simple ratios as still being consonant is that it is looking within a range of tolerance in the frequency domain.

The ratio system is not applicable to an entire scale of a key but instead only on a single pitch basis, meaning that when you shift note/pitch of a melody or the root of a chord within a key the latter ratios no longer apply but the ratios have now shifted to the new note in use.

I can't see how this is generally useful.

If a player plays multiple notes at once, which one of those is "the new note in use"?

If a player plays a monophonic passage that remains within key, and then plays a note that sounds dissonant compared to previous notes, how do you explain that?

You don't seem to be accounting for human memory at all, or allowing space for the idea of a tonic being 'established'.

You seem to have jumped from talking about observations about two simultaneous unchanging pitches to trying to apply those to pieces of music with multiple notes being played at different times. I don't think you can do that in such a simplistic way. In my opinion, you'll need to do some more research into the role of human memory, and the passage of time, in the perception of consonance and dissonance before you can get to any kind of 'general theory'.


I may sound a bit critical here - but I do think it's admirable to try to understand harmony from first principles! I just think it gets a lot more complicated than the ideas you've discussed can explain.

  • I haven't really focused on the human ear like I have on the science because I think the science by logic will translate flawlessly to the ear. To answer your question "if I player is playing multiple notes at once, which is the new note?" Well the note ratios would change each chord focused on the chord root note to build upon each chord. I also mentioned the concept of emphasising the tonic of a scale by using the ratio system only within intervals that exist within the key and discarding the others unless I'm trying to modulate key. That to me seems as straight forward as one can assume. – Seery Jul 12 at 15:15
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    "the note ratios would change each chord focused on the chord root note to build upon each chord" - yes, but how do you know what the "chord root" note is, based on the ideas that you present in parts i, ii, and iii here? – topo morto Jul 12 at 16:02
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    "I haven't really focused on the human ear like I have on the science" - I would think that the most applicable science to this subject is the science of how the ear works! If you are looking into things at this level of detail, I would very strongly recommend studying how the ear works. – topo morto Jul 12 at 16:04
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    Maybe it would be better to consider just static (not time-varying) consonance and dissonance under your 'consonance and dissonance' section, and deal with your section iv) under the 'Tension and Resolution' section, which seems to relate better to varying consonance and dissonance over a time base. – topo morto Jul 12 at 16:07
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    "I would use the ratios of C to decide my next chords root note" - but the levels of consonance/dissonance for those ratios have been observed from simultaneous notes. Why do you think it's valid to use that same set of ratios for successive notes? – topo morto Jul 12 at 20:22

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