When you add MIDI files to your cart, you should now see "0" as the price.
The problem is, you are now seeing something like "$7.50, or $15.00 for example.
We get this question asked often - and it always leads to the same answer : You are NOT LOGGED IN.
If you are not logged in, you will be treated as a "customer" with the option to purchase. Obviously you do not want this (since you can download for free as a member).
So LOG IN, add to cart, and your problem will be solved.
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If you cannot log in, please refer to this FAQ: I Can´t Log In