And I really wish I knew the answer

As a teenager I came across an LP called A tribute to hendrix, it was recorded by a guy called ' The Purple Fox ', unlike the ' late great Jimi ' he kept his tuning orthodox.

I used to jam along to 'Hey Joe' for hours, the chords were: C,G.D,A,E, all the way through.
I found I could play E minor pentatonic over the whole song.
I have since learnt from this site that there are four extra notes that can be played with Pentatonics - providing they are played immediately before a pentatonic, or between pentatonics- play them on their own or at the end of an expression and they sound wrong.
It all seems to hinge on what the human ear is expecting to hear.
Music - funny stuff