Use a towel tucked under your arms while hitting pitch shots to help keep your arms in sync and connected with your body. This will help you achieve a more consistent and on plane swing.
Take a caddie towel and place it under each of your arms so it’s stretched across your chest. Make a short swing with your club about waist high. If your arms separate from your body on the takeaway, then the towel will drop to the ground.
The goal is to get to the point where the towel is secure and your club is parallel to the ground at your waist on the backswing. If you can do this consistently and swing through to a waist high finish without dropping the towel, then you have achieved the proper arm connection from the body.