Looking for online drum machine!!?!

hi, i play bass and i really want to play with some drum beats but i dont want to spend 300-400 dollars on a drum machine!. I am looking for an online drum machine that you download onto your computer and you can make beats and stuff!. I have a mc os x macbook if that matters!. Best answer to someone who gives me the best site/download/whatever you call it!!!Www@Enter-QA@Com

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