This paper describes results about the development of a repeatable and configurable robotic finger designed to pluck harp strings. Eventually, this device will be a tool to study string instruments in playing conditions. We use a classical robot with two degrees of freedom enhanced with silicone fingertips. The validation method requires a comparison with real harpist performance. A specific experimental setup using a high-speed camera combined with an accelerometer was carried out. It provides finger and string trajectories during the whole plucking action and the soundboard vibrations during the string oscillations. A set of vibrational features are then extracted from these signals to compare robotic finger to harpist plucking actions. These descriptors have been analyzed on six fingertips of various shapes and hardnesses. Results allow to select the optimal shape and hardness among the silicone fingertips according to vibrational features.