To record music from my piano, i want to connect my piano to my multi mixer (via midi) and then from my multi mixer to my apple mac, everything so far is fine apart from i just brought a midi cable and it has 5 pins on both ends, whereas my multi mixer has 3 pin midi slots, is there some sort of adaptor i'm meant to be using or a specific wire? I can't find any 3 pin to 5 pin midi cables. Help!