When we encounter a particularly unstable piano, with great pitch deviation from season to season, a humidity control system must be considered as one possible solution. For the installation of the dehumidification heat rods in grand pianos there are suggested configurations available directly from Dampp-Chaser, as well as our own preferred arrangements gained from experience. I have found that by "triangulating" the heating elements under the soundboard, I have successfully stabilized even some of my customers' most difficult instruments. I try to install 3 48 inch-50 watt rods whenever possible --- one behind the belly rail (usually above the lyre), one diagonally (directly beneath the long bridge), and a third one attached to the long beam which runs parallel to the straight (bass) side of the case. Of course, some pianos have unusual beam patterns and some adaptations must sometimes be made (such as a shorter rod of lesser wattage), but in general I have found that by placing the heat rods in this triangular configuration, the greatest area of the soundboard can be effectively dehumidified, and the most stability achieved.