String tension refers to the amount of give a string has when engaged by the player. In layman’s terms, how hard is the string to pull? Higher-tension harps mean the strings are harder to pull (less give) and lower-tension harps are easier to pull (more give).
String tension varies between different models of harps. There’s no right or wrong with string tension. Higher (or lower) is not better, but depends on the size harp, the maker, and the player’s needs. Pedal harps tend to have higher string tension than most lever harps, due to size and string length. Some harps have lighter string tension for particular playing styles; for example, Paraguayan harps have very light string tension, which is required for that playing style.
The string material is part of the equation when you’re looking at tension. There are three several different types of strings for lever harps:
Nylon monofilament strings – the most common type of string, nylon strings are what most harpists are familiar with. Their tension varies on the spectrum from low to high. You can have a high-tension, nylon-string harp, or a low-tension one. Nylon strings tend to be the easiest on a player’s fingers.
Gut strings – Gut is the standard string type for pedal harps, and it has made its way into the lever harp world. Gut tension is much higher than nylon, and is often thought to have a warmer or more mellow sound. Some Celtic harps have traditionally been gut-strung.
Fluorocarbon strings – Fluorocarbon strings are medium to high tension in nature. Some people prefer fluorocarbon strings due to their resonant quality and durability. Both gut and fluorocarbon require more pull strength, and consequently will affect a player’s fingers accordingly.
Important note: NEVER change the strings on your harp to a different type of string without consulting your harp maker first. Changing the tension on your harp could affect it’s structural integrity, and cause damage.
The best way to see what type of strings you like is to try them! Make sure that you try the same type of strings on different harp makes and models, so you’re not just evaluating the harp itself, but how the strings compare between models. When in doubt, go with your harp maker’s suggestion on the strings that work best on that harp.