Are you sure that it's muscle pain, as opposed to joints or tendons? I have calcific tenditinis in both my shoulders. It was acute in the right shoulder, which meant that it was at a level even doctors call "excruciating" and I couldn't use my right arm for a month (during which I was totally conked out on painkillers), but in the left shoulder it's chronic and grumbles from time to time. It shows up on x-ray.

Anyway, while there's not much I can do for my particular shoulder problem apart from keeping it mobile, but one thing that helps a bit is using the Miracle Ball Method for the surrounding muscle pain that inevitably builds up when something is iffy in or near your back. Read up on it on Amazon. It's cheap, very effective, also useful for relaxation, and very easy, as it basically involves lying on a grapefruit-sized vinyl ball and doing deep breathing.