Brent, there is no one alive that can make coyotes howl at any given moment. Sometimes they will respond, and sometimes they won't. It sometimes may take them several minutes before they respond, and I have read that this is because they may be repositioning themselves before doing so, such as possibly moving toa higher location, or possibly back into thier core areabefore they respond.
I have had my best success of getting them torespond to the group yip howl on my Fox Pro. Some people use sirens and have good success. You can also getresponses from simple lone howls, two or three howls then wait several minutes and then repeat and give them a few minutes to respond. It seems thatin the west,coyotes are more willing to respond than in the east, for what reason, I'm not sure. But it's not uncommon to hear coyotes howlingin the mid-morning or early afternoon out here although for locating purposes just after dark and just before sunrise are good times to do some locating!