There are some situations when a slow retrieval works best for pike and muskies. At other times cranking a lure as fast as you can is the way to go. I like to do both on the same retrieval. A great way to trigger pike and muskies is to begin your retrieve very slow, then gradually wind faster all the way back to the boat.
This works especially well for spinnerbaits, spoons and crankbaits. Many strikes occur during the second half of the retrieval. Something about the increase in speed during the retrieval excites pike and muskies. It might resemble a fleeing baitfish. Or maybe you just have a better chance of finding the retrieval speed the fish are looking for when you change it throughout. Either way, this approach catches a lot of pike and muskies.