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Re: [SIGMusic] Melody Generator



Hey John,

Thanks for the feedback!

As it is, we are constructing the melody using notes from one of the seven diatonic scales. The particular scale is determined by the current state of happiness. The seven are ordered hierarchically like so: Lydian ("happiest"), Ionian, Mixolydian, Dorian, Aeolian, Phrygian, Locrian ("saddest").

After messing around a bit with the minor-7th, the idea of using notes from chords instead of scales seems very appealing because they seem to have a more well-defined relationship. If I could somehow determine the relative mood of at least four or fifth different chords, we may be able to implement this into the program.

Do you have any suggestions as to other chords that we could use for this purpose?

I'm going to try and look for a local copy of The Jazz Piano Book by Mark Levine to use as a resource for this task, as I remember it being quite comprehensive in its discussion of voicings.

- Joe

On Fri, Feb 24, 2012 at 1:41 PM, John Watson <jwatson5775@xxxxxxxxx> wrote:
Yeah this is a good start for some info.  I'm actually a semi-professional musician myself and have written a fair amount of songs, so if you have more questions or want more info, just let me know.  One thing that I can add now is that the intervals you have listed as "strongly consonant" (except for "+5") make up a the major chord.  However, in jazz, we use these things called minor-7 chords and many other really cool ones that sound way better than the standard major chord.  To make a minor-7th, you would use 0, +2, +7, +10, +12.  Sounds awesome, like Miles Davis.  Also another main theme is that musicians don't measure in half steps, they measure in notes of a major scale (noted in your bullet list below, in parentheses).  Now, in a major scale there are 2 places where the next note is not a complete step (2*1/2 steps) but only a half-step.  These occur b/w 3 and 4 and also 7 & 8.  8 is the upper octave of the root (+0, in half-step notation).

For more info, just let me know, or look up any beginner jazz book, which goes appropriately deep into the theory. (appropriately deep=enough to make it sound cool, without bothering with all the non-important details that classical musicians like to argue about :-)).

+John Watson




On Mon, Feb 20, 2012 at 17:39, Joe Betz <joebetz91@xxxxxxxxx> wrote:
Hey Alex / sigMusic list,

Some notes I jotted down while perusing a first year music theory book and fiddling around on a keyboard the last couple of days. I hope the formatting helps make the length bearable, I'm just trying to put everything on the table I've found that we could possibly work with.

  • As for the essential task of constructing a melody that to some degree euphonic, here are a few musical ideas that we could consider:
  1. Tonality: the melody should create some sort of pull towards a specific pitch (the "tonic"). This can be accomplished by either one or a combination of the following methods: 1) simply referencing the tonic more often than any other pitch, 2) placing the tonic at key points within the passage (such at the beginning, end or any strong metrical point (e.g., downbeats), 3) using other pitches that support and reinforce the tonic harmonically (such as the perfect 5th above or perfect 4th below), or 4) tying pitches that are one step away (usually below) from the tonic in shorter rhythmic phrases (such as a sixteenth note immediately preceding it
    • There is risk of the melody becoming overly tonal, so it would also be good to set restrictions, perhaps via a counter, that would make sure that a note isn't used too much in any given segment of the four bar phrase.
    • Creating a less tonal melody may be effective in expressing confusion, though it may only succeed in stripping it of any emotional connotations whatsoever. Good old trial and error should serve us well here.
  2. Intervals: the use of consonant and dissonant intervals may be an easy way to express peace and struggle accordingly, though these two feelings don't correspond directly with any of our mood parameters (damn human psyche...). Regardless, it'll probably work fine as long as we have other factors to reinforce them. When choosing the next note in the series, the algorithm could adjust the probability of which interval is used according to  the location of the preceding note and the current happiness level (certain intervals may be exclusively reserved for certain emotional state).
    • Larger intervals create more space (which in turn yields clarity and placidity) while smaller intervals tend to muddle things up. This could work well for our confusion parameter.
    • Here is a little schematic of the relative consonance / dissonance of the most commonly used intervals:
      • + 0 half-steps: strongly consonant    (1, root)
      • + 1 half-step: strongly dissonant
      • + 2 half-steps: mildly dissonant        (2nd)
      • + 3 half-steps: consonant                 (minor 3rd)
      • + 4 half-steps: consonant                 (3rd)
      • + 5 half-steps: strongly consonant     (4th)
      • + 6 half-steps: dissonant
      • + 7 half-steps: strongly consonant    (5th)
      • + 8 half-steps: consonant
      • + 9 half-steps: consonant                 (6th)
      • + 10 half-steps: mildly dissonant       (minor 7th)
      • + 11 half-steps: strongly dissonant    (7th)
      • + 12 half-steps: strongly consonant   (1, root)
  3. Phrasing:
    • As far as I can tell, the easiest way to frame the melody as one complete thought would be to use the same intervallic distance at the beginning and end of the four bar phrase. This will give it a sense of finality, which could be something we reserve for more logical emotional states.
    • In order to weave together the individual measures, we could insert "cadences" (rhythmic and/or tonal punctuation) at the end of each, and have it so the first three are less conclusive than the final. For example: the first three measures could end with an eighth note on the perfect 4th or 5th, while the final measure ends with a quarter note on the tonic.
    • The contour of the melodic line can create a feeling of tension / motion (excitement) if going up and relaxation (boredom?) it going down. Dynamic changes can also help create a sense of motion, though I was thinking it'd be best to keep them gradual so that we can simply modify a general direction
    • The rhythm and melody of the first measure could be used as a template for the other three, so that (as you suggested) they are in some way related. I'm gonna need to spend some more time studying the concept of variation before suggesting an algorithmic method to emulate it, but in any case we're gonna need some way to store information about the first measure so that it can be accessed while generating the others.
  • Once we can get the program to output a melody with solid structure, tweaking its tempo, timbre and octave placement should be a fairly easy way to signal the different moods.
    • Happiness / Sadness (octave placement, chorus effect)
    • Excited / Relaxed (tempo (I'm thinking 90 - 120 bpm is a good range), articulation)
    • Random / Logical (distortion / bitcrusher)

If any of this needs clarifying, let me know. I'm just getting my head around a lot of this music theory jargon myself. Fortunately I've found a pretty good reference, so I could probably elaborate if it'd help.

- Joe



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--
JOHN WATSON EIT, MSCE
UIUC College of Engineering, USGS