Fig. 6 in U.S. Patent 10,810,987 shows a 12-way electric guitar pickup switching circuit for 3 matched single-coil pickups. One can easily pick the strings for each circuit and get an amplitude spectrum with freeware like Audacity. One can easily pick single strings or rack the pick across them all. One can fret the strings or not. One can easily calculate the mean frequencies, or even spectral moments of such signals. One can apply A-weighting or not to the spectra.

But how can any of that be made to make sense to musicians as a measure of tonality?

Are there any usable standards of comparison between frequency spectra and a musician's description and understanding of tonality?