Steve Moss, Moss Piano Service

Several factors govern how often you should be calling your piano tuner. In the next several posts, we’ll cover each one in turn. Today’s focus is on seasonal  changes.

Piano soundboards swell and contract depending on the temperature and relative humidity in their environments. Since the soundboard is fastened to the instrument’s case around its edges, but left free to vibrate everywhere else, seasonal changes are more pronounced in the piano’s midrange than at the bass and treble ends.

Piano soundboards are built with a slight amount of “crown,” or a slight convexity toward the strings. The presence of a crown creates tension on the board and is believed to enrich the piano’s sound. Since the board is naturally curved toward the strings, as it swells in humid conditions, it will swell further toward the strings. This swelling pushes against the bridges on which the strings rest, causing the strings’ pitch to rise slightly.

In practice, this means that during humid summer months, a piano’s midrange will tend to go slightly sharp relative to the bass and treble ranges. In cooler weather, when heating systems are in use, the air becomes significantly drier, causing the soundboard to flex away from the strings, thus lessening the pressure on the bridges, and lowering the strings’ pitch in the midrange, causing them to sound flat relative to the bass and treble.

This effect is more pronounced in climates with warm, humid summers and cold, dry winters, such as in Milwaukee, where I live and work. In more constant climates, such as in the drier areas in the Western US, seasonal change has less of an effect on piano tuning.

Because of the effects of seasonal change, piano tuners generally recommend having pianos tuned twice per year for optimal performance year-round. A lot of people have heard that you should have your piano tuned once in the summer and once in the winter. The optimal times to tune pianos tend to be in late fall after the heat has gone on, and in late spring, after the heat has gone off.

Since there aren’t enough piano tuners to tune every piano in town during the optimal weeks or months mentioned above (and what would we do with ourselves the rest of the year?) many tuners develop techniques to compensate for the effects of seasonal change. Depending on the time of year, your tuner may tune your piano just a shade high or low in the midrange, so that when it rises or falls with the seasons, it will not go as far out of tune. This  compensation will be so slight that your ears won’t notice it, and as the climate changes, the piano will remain in better tune. There is no need, then, to worry about calling the tuner at exactly the right time. If you put your piano on a twice-a-year tuning schedule, your tuner will keep it sounding as consistent as possible.