  The evolution of different types of quasi-periodic oscillations (QPOs) and
the coupled radiative/physical changes in the accretion disk are still poorly
understood. In a few black hole binaries it was found that fast evolution of
QPOs is associated with spectral variations. Such studies in other black hole
binaries are important to understand the QPO phenomenon. For the black hole
transient XTE J1817-330, we study fast QPO transitions and accompanying
spectral variations to investigate what causes the spectral variation during
the QPO transition. Roy et al. (2011) found QPOs in ten RXTE observations of
XTE J1817-330. We found that, among the ten observations, only one observation
shows erratic dips in its X-ray light curve. The power density spectra and the
corresponding energy spectra were extracted and analyzed for the dip and
non-dip sections of the light curve. We found that type-B $\sim$6 Hz QPO
changes into type-A QPO in a few tens of seconds along with a flux decrease.
This transient evolution is accompanied with a significant spectral variation.
We report a transient QPO feature and accompanying spectral variation in XTE
J1817-330. Based on our findings, we discuss the origin of fast evolution of
QPOs and spectral variations.
