It's more-or-less a diminished chord, passing between G and D major
chords. The curves show the harmonics-- multiples of the
They converge at a high D#, probably perceived as a
slightly dissonant color tone. It's the 4th harmonic of the B,
the mysterious 7th harmonic of the F, and (maybe irrelevantly? it's
rather distant) the 18th of the bass note C#.
Also interesting is the F/F# at the top of the treble clef, where
harmonics converge more sloppily. Again, color sound, but
wider and more contoured energy train.