  We investigate the behavior of the high frequency quasi-periodic oscillations
(QPOs) in 4U 0614+091, combining timing and spectral analysis of RXTE
observations. The energy spectra of the source can be described by a power law
(alpha ~ 2.8) and a blackbody (kT ~ 1.5), with the blackbody accounting for 10
- 20% of the total energy flux. We find a robust correlation of the frequency,
nu, of the higher frequency QPO near 1 kHz with the flux of the blackbody,
F_BB. The slope of this correlation, dlog(nu)/dlog(F_BB), is 0.27 to 0.37. The
source follows the same relation even in observations separated by several
months. The QPO frequency does not have a similarly unique correlation with the
total flux or the flux of the power law component. The RMS fraction of the
higher frequency QPO rises with energy from 6.8 +- 1.5 % (3-5 keV) to 21.3 +-
4.0 % (10-12 keV). For the lower frequency QPO, however, it is consistent with
a constant value of 5.4 +- 0.9 %. The results may be interpreted in terms of a
beat frequency model for the production of the high frequency QPOs.
