Singing in the shower takes on a new dimension when you're accompanied by a whistling shower head. No matter how you vary the pitch and stay in tune, the screech from the shower head just won't play. A poor melody is one thing, but water sprays and streaks to one side or the other are a real problem. This problem is normally caused by a buildup of hard water deposits inside the small openings of the shower head.
Once they become partially plugged, the squealing starts and the uniform spray is blocked. Solve the problem by soaking the shower head in a plastic storage bag filled with vinegar or a hard-water-scale removal product. Often you can just fill the bag and tie it around the pipe that feeds the shower head. Follow label directions for any chemical you use. After soaking the shower head, rub it with a coarse cloth or use a toothpick to clear away residue and hard deposits.
To make the job easier, you can simply remove the shower head by turning the connector counterclockwise. This may require using a small wrench or pliers: protect the chrome plating by placing a rag under the wrench.