The basic idea here is to chose a source od simplicity and invarious degrees in time more complexity and returning to the simplicity. Thus SIMPLICITY->COMPLEXITY->SIMPLICITY , ETC and also by REPETITION , ASSIMILATION, INNOVATION . THE MAIN CONCEPTIS TO CREATE A "FLOW" AND REMAIN INTHE "FOW" A TERM OF PSYCHOLOGY THAT DESCRIBES THE FLOW OF ENERGY AND CREATIVE FORCE FROM THE IMMORTAL SOUL TO THE MORTAL PERSONALITY . The improvisation with such a melodic percusion instrument like a handpan or tongue drum (which is much like a metallophone) is the 1st type of improvisation (single instrument and unpredictable rhythm, unpredictable harmony, unpredictable melody ) as in post 295.
We should not forget of course the 3 principles of improvisation as the post 295,
BASIC PRINCIPLE 1=HARMONY POLARITY
BASIC PRINCIPLE 2: MELODIC MONOTONICITY-VARIATION POLARITY
BASIC PRINCIPLE 2: THE BIOWARE OVER THE HARDWARE.
For analysis of these 3 principles see post 295.
THE 4 SOURCES OF SIMPLICITY AND CO9NSTANTS REPETITIONS ARE
1) RHYTHM CONSTANTS(GROOVE) (We keep the rhythm invariant and we shift
it over the musical notes and octaves)
2) ASCENDING-DESCENDING-STAYING SHAPE OF A MELODIC THEME CONSTANTS (We keep
the melodic theme shape invariant and we translate in the scale , or invert it
or elongate it)
3) A BASS LOOP THAT REPEATS (OSTINATO CONSTANTS) (We keep a bass
loop invariant and we enhance it with melodic themes)
4) ONE OR TWO CHORDS ALTERNATION (CHORDS CONSTANTS) (We keep the
harmony of the 1or 2 chords invariant and we create parallel fitting melodic
themes)
Here is a video by a nice girl and improviser who explains these 4 sources of simplicity
https://www.youtube.com/watch?v=PEuwaKR0cbY&ab_channel=AmyNaylor
