I learned this from a K9 officer who has a cadaver dog who's on a long leash or walking free when working. She's a take home dog so she gets lax sometimes.
He continuously calls her in a monotone but loud voice. So literally continuous without break until he sees a change like she turns her head. When she does, he initiates the recall. I've seen him do it, it's annoying. But it works.
Have done it with my dog with some success. One time she took off and I didn't have a good hold on the leash and this worked to stop her chasing. But most of my success with recalls off the leash have been attributed to having hot dogs ready. I only give her hot dogs for recalls. Her recall rate with hot dogs in hand are at like the high 90 % range when we are at parks, dog parks, and hiking.