Recording With Standard Audio Card? Options

[MOLLOWITZ]

for the longest time i've been trying to record midi into ProTools, then bounce it to a disk and burn it off... i've been trying to explain to anyone who would listen what i was trying to do, and what i had already tried. someone was perceptive enough to tell me that midi is NOT audio! so- now understanding what i previously thought that i knew, i continue my search for a way to directly interface my kurzweil 2500x with my imac.
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moving on- my question now is this: how to i directly interface my kurzweil 2500x into my imac using the standard audio (line-in) card? is there some sort of adapter i need to purchase? or do i need an entirely new audio card? please advise.

thanks.

-cody