I use a Johnny Stewart tape of a hawk & crows fighting, & it works real well as long as you stay concealed & don't wear bright colored clothing or hats.
I always have much better luck in the spring. I think there are a lot more young, dumb birds at this time. (not really sure if it's legal in the spring here in Indiana)
If you just want to shoot a LOT of crows, I've found a place down in the river bottoms where they roost, & 4 or 5 of my buddies will walk under the trees right at dusk & blast 5 or 6 with each shot----every night! Not sure how legal that is either. It is very effective!