VST Drums

[Keys1970]

Drum machines (Boss DR-770, Alesis SR-16) have a drum fill button that triggers the drum fill pattern that is associated with the main drum pattern. Arranger type keyboards (Korg EK-50, Korg Pa5X) have the same type of drum fill button. As I study VST drum software (EZ Drummer 3, and others) I don't see an on-screen button/graphic to trigger a drum fill pattern during the playback of the main drum pattern (via Mouse, QWERTY, MIDI device). It seems to me that VST drum software provides many drum patterns and many associated drum fills; however, there is no way to trigger a drum fill during the main drum pattern. The user has to drag in the main pattern, then drag in the fill pattern, repeat/loop, etc. Am I missing something? I like the physical buttons (Start, Main (4 variations), Fill, and End) on the Boss DR-770 and Korg EK-50; however, their selection of drum patterns is quite limited compared to what VST drum software (say, EZ Drummer 3) offers. Thoughts?