[Raro]

Thanks for that! This is right up my alley. The signal separation makes sense, as the three pick-ups each provide a different sound, but none emulate the live experience quite so well.

The under-the-saddle piezo acts as an accelerometer right at the termination point of the string. So it gets every partial without any real damping, so they tend to sound far too bright. You're directly picking up vibrations that tend to be damped by the time they go through the impedance matching system that is a live guitar (i.e. acoustic radiation from a few feet or more in front of the soundboard). Fishman often roll their piezos off a lot to de-emphasize the upper partials, because it sounds so bright.

The humbucker is effectively a velocirometer, and is around a quarter of the scale length along, so it sounds a lot more mellow than the piezo, but picks up on different things. It also doesn't get the damping that the string-wood-air interface tends to bring, and also doesn't pick up on the neat interactions the instrument has with the internal and external air elements (for example, the Helmholtz and pipe modes of the air in the internal cavity).

The internal mic does sample the interaction the guitar has with the air. But it misses out on the higher radiation modes, which tend to be radiated out the front of the guitar. So it sounds very 'boomy'. It's convenient, for a mic, but doesn't sound great by itself.

In combination, these sound pretty good! But still doesn't emulate the 'real thing'. Hence Jon also mentions the use of external mics too. That, in addition to the separate channel for the octave pedal!