Disclaimer - I'm only talking as a 4 string bass player.
Ok. I did some head scratching and was thinking of a way to memorise it all in regards to pentatonics and uding them for on the fly improv... In no way do I claim it's a revelation or anything. If at all - it's just me trying to put it all into a visual framework to enable me to memorise and access it on the fly without getting lost. Now I am asking for people to look at my idea and maybe give it some critique? However I do ask if you critique - can you just say where my idea falls apart? I'm working on ironing it out...
But if it's annoying I can take it down... As a person who thinks visually in geometric pattern approach to anything that needs memorization I came to the following approach. If we talk in general then mode shapes as Charles Berthoud (from his Patreon) mentioned are traveling along the neck. If we visualize them abstractly then any given minor pentatonic mode can be generalized as the following shapes:
Legend: |-| represents section on fret board between frets
1 st mode
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2 nd mode (lowest note 3 semitones above root)
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3 rd mode (lowest note 5 semitones above root)
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4 th mode (lowest note 7 semitones above root)
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5 th mode (lowest note 10 semitones above root)
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Also noticed that there is a mirror symmetry around the 3rd mode which essentially is a "box" or rectangle. In other words 5th mode is a mirror inversion of 1st mode. 4th respectively of 2nd. Using this approach and knowing each fret is a semitone I found it easy to get the correct fret numbers of any mode of any minor pentatonic. Say for example take 4th mode of C minor. Root note is A string 3rd fret. Lowest note of it's 4th mode is fret 10 on A string. Using the shape diagram (which should be memorised) 10 fret -> 3 frets above on first string (in our case A string) is fret 13. Same for D string. G string it's only 2 frets above - i.e. 12 string. And indeed it matches the tabs for 4th mode for C minor:
G string 10 - 12
D string 10 - 13
A string 10 - 13
To jump to a major pentatonic it appeared to be extremely easy actually. The second mode of the Minor pentatonic gives you first mode of its relative major pentatonic. So 5th mode of any given minor pentatonic gives its relative major 4th mode pentatonic and so on. In other words one could also say for any given minor pentatonic it's relative major pentatonic root note is just three semitones above that minor key root note.
Offcourse this all works neatly on a 4 string and I'm only talking 4 string bass. I've yet to come up with something similar for other key modes such as Lydian Phrygian and etc.
As I said - I'm posting here NOT as an intent to preach. I'm a noob - I'll say straight. The only reason I'm posting this all is I'm needing a few fresh pair of eyes to look at this idea and give a fresh review/critique. I don't have local bass or much musician friends locally for that matter to discuss all of this in depth. Many thanks in advance for your patience in reading this whole load of thoughts 😁