Spalding,
I cannot recall what if anything you could adjust on the Korg and Roland keyboard's drum kit sounds, mainly because I didn't have either long enough to dig deeply into the OS of either. On Yamaha keyboards, however, you can adjust a number of sound parameters on each component of any style. If's an onboard style you can save the settings to a registration, or run the style through the keyboard's onboard style creator program, make the changes and save the style as a user or third-party style. If it's a third party style to begin with, you can save the changes directly to the style without going through the style creator program.
If you look under the lessons tab of the PSR Tutorial's home page you'll find detailed instructions of tuning style files.
Cheers,
Gary
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)