The other gods would be the other voices. The most famous instance was when Israel rejected the leadership of the LORD, so they could have a king like other countries. (I Samuel 8:7) That was how Saul become the first king of Israel. He was a god in competition with the LORD. His was another voice besides the LORD's, and he was the beginning of many problems for Israel. It is a good analogy to the way church people tend to aggregate around strong personalities. Lets say you like pastor Ben, because he's very wise and quiet but your brother likes Adam, because he's always pushing to feed the hungry. At some point you may be put in a position where Adam disagrees with Ben and feel pressured to take one side or the other. At that point you can be sure you are listening to another voice besides the LORD's, because you now have a king.To listen to the voice of a stranger is the same as to bow down to other gods and worship them. Why voice and not word? I think it is because the stranger has most of the same words but the words are counterfeit words, thus they can be discerned by anyone loving Yahweh with the whole heart.