(this post has not been written completely yet)
This improvisation technique is from old civilizations like in the Chinese harps , Greek Kanon or Kanonaki or Sandouri, eastern kanon (qanun) , etc when the concept of chord was not discovered or invented yet as widespread tradition in the music. We do not mean here the simultaneous sounding of 2 or 3 or 4 voices in harmony.
See also post 102 , 111 , 118, 197.
And a relevant video of two parallel melodies music
https://www.youtube.com/watch?v=OcHWvl16mpg
The next is a rather funny but beautiful example with the ukulele band playing same chords but different well known melodies that still fit!
https://www.youtube.com/watch?v=0HuSx3z0E6g
Some rules of compatibility of the simultaneous or alternating melodies
This improvisation technique is from old civilizations like in the Chinese harps , Greek Kanon or Kanonaki or Sandouri, eastern kanon (qanun) , etc when the concept of chord was not discovered or invented yet as widespread tradition in the music. We do not mean here the simultaneous sounding of 2 or 3 or 4 voices in harmony.
See also post 102 , 111 , 118, 197.
And a relevant video of two parallel melodies music
https://www.youtube.com/watch?v=OcHWvl16mpg
The next is a rather funny but beautiful example with the ukulele band playing same chords but different well known melodies that still fit!
https://www.youtube.com/watch?v=0HuSx3z0E6g
Some rules of compatibility of the simultaneous or alternating melodies
The basic rules are the next 2
RULE 1 NON-DISSONANCE The main (possibly human voice ) melody and the instrumental counter melody have intervals of simultaneous sounding that statistically are more of 3rds 4ths/5ths, 6ths and 8ths or larger compared to those by 2nds. Thsi may include that one of them is chord-arpeggio, but it is not necessary. Also they may sound simultaneously or sound by pieces in an alternating mode.
(See also post 112 about the harmonic statistical profile of a melody)
RULE 2 SIMPLE-COMPLICATED The one of the two melodies is monotone simple and repetitive, like percussion or drone melody or chord-arpeggio , while the second is more complicated and changing.Some times the simpler may be simply strumming an interval of the scale that contains the parallel melodic theme, but maybe on different octave. If the instruments is a piano or digital keyboard, or an harp, or a Kanun (Qanun) or a Sandouri played by the fingers, then is is convenient to play the simpler melody with the left hand, and the complicated with the right hand.
RULE 3. BASS-LINE OR SOPRANO DRONE The simpler repetitive type of melody can be at higher octaves compared to the more complicated melody or it can be a kind of bass-line in lower octaves.
RULE 4. KITE-LIKE THEMES. Usually but not always the simpler type of melody may be a melodic simplicial sub-melody (like drone melody) of the melodic centers of the more complicated melody, or an homemorphic variation of it. If there is also a chord progression it may be the harmonic or the chromatic simplicial sub-melody. For this to work better the complicated melody might consists from melodic themes that are kite-like with a tail and a head. In other words the tail is a path that is waving or straight (Dolphin-words) that ends on a longer and louder sounding note (Head) which is a local center of the melodic theme. We remind that the basic structure of the melody is through melodic themes (see also post 101 about Dolphin-words). Each melodic theme must convey a musical meaning as simple proposition has verb that expresses some action-motion subject and object (see posts 27 and 40 about melodies as language).
RULE 4. KITE-LIKE THEMES. Usually but not always the simpler type of melody may be a melodic simplicial sub-melody (like drone melody) of the melodic centers of the more complicated melody, or an homemorphic variation of it. If there is also a chord progression it may be the harmonic or the chromatic simplicial sub-melody. For this to work better the complicated melody might consists from melodic themes that are kite-like with a tail and a head. In other words the tail is a path that is waving or straight (Dolphin-words) that ends on a longer and louder sounding note (Head) which is a local center of the melodic theme. We remind that the basic structure of the melody is through melodic themes (see also post 101 about Dolphin-words). Each melodic theme must convey a musical meaning as simple proposition has verb that expresses some action-motion subject and object (see posts 27 and 40 about melodies as language).
RULE 5. We may go as far as utilizing this method as a method of creating adoptions or remix of a song. This requires that the improvised melody will fit only to a percentage x%<50% with the parallel sounding song and the rest 100%-x% the melody , rhythm and chords will not fit and will be the innivated adoption of the song (according to our inner emotional impulses and habits) . Of course the overall result of the underlying song and its adoptoion will not be audible with good feelings as they will be incompatible , but the intention is to be inspired in real time by the song and create in real time an adoption of it. Finally oly the adioption will be presented not the parallel initialinspiration.