EZDrummer is basically a drum only sampler that uses midi triggering to play real drum samples. It basically performs as any other sampler but gives you the added flexibility of multiple output via "virtual" microphones. It does not allow you to write, or load your own sample. It has no programming functions at all. It will play however any drum midi file you throw at it. If you already have midi drum sequences, it does a great job of making them sound like real drums.
If you want to program your own drum fills and patterns, you will need a separate sequencer. I would recommend a simple but free program called DrumFlow to write short midi files. If you've got some money and time to spare look into Cakewalk/Sonar/Fruity Loops for PC, or Logic for Mac.
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