Over the years, a trained musician develops the ability to produce a sound as desired: the player's gestures are precisely executed, in order to control each note. In the case of the concert harp, a previous study had underlined the characteristics of string plucking, both highly reproducible and player-specific. However, the whole harpist's body is obviously also involved in a musical performance. Therefore, the present paper investigates the player / harp interaction, by characterizing the musical gestures in relation to the musical interpretation. We have captured the motion of three skilled harpists playing Debussy's Danse Profane, using a tracking system based on infrared cameras. Acoustical signals have been measured synchronously. A set of acoustical and kinematic descriptors has been extracted from the collected data. They provide features of instrumental gestures (directly related to the sound production) and ancillary gestures (not directly involved in the sound production). Results indicate that instrumental gestures have common characteristics from one player to another, while ancillary gestures are specific to her/him. It is also shown that harpists perform remarkably reproducible gestures. Finally, the analysis of the harpist's strategy highlights the relationship between physical properties and the objectives of harp performance.