Guitars and violins go sharp in the Spring because humidity returns. Humidity is the amount of moisture in the air. It’s measured as a percentage and expressed as “Relative Humidity (RH).”

As the Northern Hemisphere heats up this time of year, moisture in the air returns from winter. When the air is saturated, it is measured as 100% and rain is produced.

Moisture in the air is absorbed into wood products, such as acoustic pianos, guitars and violins. Consequently, wood expands and increases the tension on the strings, which causes the strings to rise in pitch and sound sharp.

Modern tuners are helpful for quickly tuning acoustic guitars at the beginning of early playing session. Unlike the rest of the year, when playing a stringed instrument stretches the string a small amount and causes it to sound lower or flat, Spring and Summer tend to increase tension to the strings until being tuned.

Air conditioners and dehumidifiers can help stabilize swings in an instruments relative humidity. Most manufacturers recommend maintaining a relative humidity of 40%, year-round when possible.