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Re: [SIGMusic] Melody Generator

Yeah this is a good start for some info. ÂI'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. ÂOne 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. ÂHowever, 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. ÂTo make a minor-7th, you would use 0, +2, +7, +10, +12. ÂSounds awesome, like Miles Davis. ÂAlso 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). ÂNow, 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. ÂThese occur b/w 3 and 4 and also 7 & 8. Â8 is the upper octave of the root (+0, in half-step notation).

For more info, just let me know, or look up any beginner jazzÂbook, which goes appropriately deep into the theory. (appropriately deep=enough to make it sound cool, without bothering with all the non-importantÂdetails 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 byÂeither one or a combination of the following methods: 1) simplyÂreferencing the tonicÂmore often thanÂany other pitch, 2) placingÂthe tonicÂat key points within the passage (such at the beginning, endÂor any strong metrical point (e.g., downbeats), 3)Âusing otherÂpitches thatÂsupport and reinforceÂthe tonicÂharmonicallyÂ(such as the perfect 5th above or perfect 4th below), or 4)Âtying pitches that are one step away (usually below) from the tonic inÂshorter rhythmic phrases (such as a sixteenth note immediately preceding it
    • There isÂrisk 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 anyÂemotional 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 usedÂaccording 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 usedÂintervals:
      • + 0 half-steps: strongly consonant  Â(1, root)
      • + 1 half-step: strongly dissonant
      • + 2 half-steps: mildly dissonant    Â(2nd)
      • +Â3 half-steps: consonant        ÂÂ(minor 3rd)
      • +Â4 half-steps: consonant        ÂÂ(3rd)
      • +Â5 half-steps:Âstrongly consonant   (4th)
      • +Â6 half-steps:Âdissonant
      • +Â7 half-steps: strongly consonant  Â(5th)
      • +Â8 half-steps: consonant
      • +Â9 half-steps: consonant         (6th)
      • +Â10 half-steps: mildly dissonant    (minor 7th)
      • + 11 half-steps: strongly dissonant  Â(7th)
      • + 12 half-steps:Âstrongly 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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