For each triad root, we estimate beating in fifth and third, then derive brightness and agitation scores.
\(b_3\) is third beat-rate, \(b_5\) fifth beat-rate. Fast thirds and fast fifths increase agitation; slow fifths can keep brilliance while preserving stability.
Major: calm → bright → ecstatic → manic as beat-rate rises.
Minor: grounded → wistful → urgent → haunted/intense under the same beat-rate axis.