From a 2010 article on the 40th anniversary Jimi's death:

"“We started from the premise that music was a mission, not a competition,” says Mayer, who describes himself as a “sonic consultant” to Hendrix. “That the basis was the blues, but that the framework of the blues was too tight. We’d talk first about what he wanted the emotion of the song to be. What’s the vision? He would talk in colours and my job was to give him the electronic palette which would engineer those colours so he could paint the canvas.

"“Let me try to explain why it sounds like it does: when you listen to Hendrix, you are listening to music in its pure form,” he adds. “The electronics we used were ‘feed forward’, which means that the input from the player projects forward – the equivalent of electronic shadow dancing – so that what happens derives from the original sound and modifies what is being played. But nothing can be predictive – it is speed-forward analogue, a non-repetitive wave form, and that is the definition of pure music and therefore the diametric opposite of digital.

"“Look, if you throw a pebble into a lake, you have no way of predicting the ripples – it depends on how you throw the stone, or the wind. Digital makes the false presumption that you can predict those ripples, but Jimi and I were always looking for the warning signs. The brain knows when it hears repetition that this is no longer music and what you hear when you listen to Hendrix is pure music. It took discussion and experiment, and some frustrations, but then that moment would come, we’d put the headphones down and say, ‘Got it. That’s the one.’"