  Building on results from previous studies of Cygnus~X-1, we analyze Rossi
X-ray Timing Explorer (RXTE) data taken when the source was in the soft and
transitional spectral states. We look at the power spectrum in the 0.01 -- 50
Hz range, using a model consisting of a cut-off power-law and two Lorentzian
components. We are able to constrain the relation between the characteristic
frequencies of the Lorentzian components, and show that it is consistent with a
power-law relation having the same index (1.2) as previously reported for the
hard state, but shifted by a factor ~2. Furthermore, it is shown that the
change in the frequency relation seen during the transitions can be explained
by invoking a shift of one Lorentzian component to a higher harmonic, and we
explore the possible support for this interpretation in the other component
parameters. With the improved soft state results we study the evolution of the
fractional variance for each temporal component. This approach indicates that
the two Lorentzian components are connected to each other, and unrelated to the
power-law component in the power spectrum, pointing to at least two separate
emission components.
