  The motion of the floating bridge of the banjo, in conjunction with the break
angle of the strings over that bridge, produces string tension modulation that
is first order in the amplitude of the string motion. This note refines a
previous suggestion regarding the impact on the frequencies of the strings' and
bridge's motion. For a given mode frequency pair of string and bridge, the
resulting tension modulation produces a new, additional motion characterized by
the sum and difference of the original ones. Strictly speaking, this
corresponds to canonical "frequency modulation" only in the limit of modulation
slow compared to the string frequency. The more general result is precisely an
example of what is known as "parametric oscillation," first analyzed by
Rayleigh. The qualitative impact of tension modulation on banjo timbre remains
as suggested previously. It is only the precise math and physics that warrants
this correction.
