The original harps (as well as their replicas) provide a clear and powerful sound even with their very light string tension. Thus allows a relaxed fingering and is balm for people who need or want to protect their finger joints. In addition the narrow string spacing facilitates the fingering and playing in octaves is easy for small hands without any overstretching.
Even people with fine finger structure or after having hand injuries play the historical harps effortlessly. Brisk and sparkling passages can be played very quickly without effort and thereby the articulation is precise and clear. This fact is amazing even for virtuoso players who are normally familiar with modern concert harps.
As a comparison: a concert harp keeps a total string tension of about 1'100 kp. On a historical single-action harp this is between 250 and 400 kp depending on age and type. The octave-spacing c° - c1 is about 112 mm on concert harps, but only 92 to 100 mm on historical harps.