Put simply, string spacing refers to the distance between harp strings; string tension refers to how much “give” there is in a string.
Pedal Harp spacing (also known as concert spacing) should be more or less standard in all pedal harps and is, therefore, not something you need be overly concerned about. Just watch that the spacing is relatively even throughout the harp’s range, as uneven spacing makes it difficult to play by feel.
Lever harp spacing is nearly always less wide than pedal harp spacing and, as is so often the case with lever harps, varies significantly with models and makes. You do, therefore, need to give some consideration to the string spacing of the lever harp that you are considering purchasing.
In reality, if a lever harp is said to have concert spacing, it probably falls just short of full concert spacing, but implies that it has a wide spacing by lever harp standards. Choosing a wide spacing is a good idea if you intend to go on to the pedal harp, as there would then be minimal adjustment. Some players feel that a medium string spacing is more appropriate for a lever harp – especially those who perform in a traditional Irish or Scottish style, and certainly, many of the more idiomatic ornaments are easier to execute if the strings are closer together.
Whether you go for wide or medium string spacing is a matter of personal choice and what you feel comfortable with. However, do avoid narrow spacing. How can you tell if string spacing is too narrow? Easy: if you place your finger on a string and find that it is touching an adjacent string, then the spacing is too narrow.
As with pedal harps, pay particular attention to whether the spacing is even throughout the harp and avoid the harp if the spacing fluctuates considerably.
String tension describes how much “give” there is in a harp string. If the string stays relatively tight and in position when engaged, then it is said to have high tension. If the string moves out of position, then it has low tension.
A pedal harp will have higher tension than a lever harp. Once again, we find that string tension in lever harps varies dramatically.
It is worth giving some serious consideration to the string tension in your harp. Beginners have to work very hard to handle high tension strings, which can be cruel on novice fingers, causing blisters and soreness. However, it is the very fact that high tension strings force you to work so hard, that is their strength. Harp strings are like bicycle gears: the harder you have to work, the more you get out.
In other words, the more force you have to apply to pluck the string, the louder and more resonant the resulting sound. Very low tension strings will never be able to produce much volume or resonance.
Another problem with very low tension strings is that, if they stretch out of position too far, your fingers are in danger of hitting adjacent strings, resulting in all kinds of unwanted sounds.
In general, gut strings allow for higher tension than nylon strings. However, some makers, such as Dusty Strings, are making nylon strings with higher tension, which results in a very resonant lever harp.
Those who are starting to learn on a pedal harp do not have much choice about string tension, as tension in pedal harps is fairly standardised. However, those who are learning on a lever harp should be looking to make a compromise between comfort for fingers and a good sound. This means choosing a lever harp that has high to medium string tension, bearing in mind that even a high tension lever harp string will not be as high tension (and therefore unkind to fingers) as a pedal harp.
The exception to this would be children, the elderly, or anyone who does not possess the finger strength for high tension strings. In this case, low tension strings would be recommended.