I don't know about other brands, Diki, but with Yamaha you have an option to either have the fill come instantly, or have it wait till the next beat.

Gary cool
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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.)