Whine

I think it's the other end. The pilot bearing, if it has a bearing and not a bushing. While the clutch pedal is depressed and partially depressed, the bearing is spinning. When it is released completely, the input shaft and crank shaft are turning as one and the pilot bearing would stop making noise. The throw out bearing on the other hand, spins constantly.

I guess it could be argued either way, because the throw out bearing is under more load while the clutch pedal is depressed. I think it's a good bet that it's one or the other.