The NN-XT features a pitch detection function to help you set the root keys. This is useful if you for example load a sample that you haven't recorded yourself, and you don't have any information about its original pitch.
1. Select all the zones you want to be subject to pitch detection.
2. Pull down the Edit menu or the NN-XT context menu and select "Set Root Notes from Pitch Detection".
The samples in all the selected zones will now be analyzed, and the perceived root keys will automatically be set for you.
Note that for this to work properly, the samples must have some form of perceivable pitch. If it is sampled speech, or a snare drum for example, it probably doesn't have any discernible pitch.