The action of the soundpost in a violin is not well understood and fundamental knowledge is needed. Therefore low‐frequency forced modes, operating deflection shapes, 250–600 Hz of a violin were investigated. Harmonic, sine wave, excitation was applied via the bridge (resembling playing) or via the sound from a loudspeaker. The latter excitation gives a reciprocal measure of radiativity. The modes were investigated with TV‐holography and electro‐acoustical admittance measurements. A carefully selected violin was investigated without soundpost, with soundpost, and with the soundpost position shifted toward the centerline. Answers were sought to three questions: Which are the violin modes forced via the bridge? To what extent do they radiate sound? What is the action of the soundpost? The observed modes were mostly not pure normal modes but mode combinations. Generally there is a nodal line close to the soundpost position of the plates. Schelleng has hypothesized that the main action of the soundpost is to make the violin nonsymmetric. The first top plate mode with soundpost can be looked upon as a combination of the first symmetric top plate mode and the first asymmetric mode without soundpost. The first mode is an efficient radiator and the second mode transfers the string vibrations via the bridge to the top plate efficiently. The asymmetric first mode with the soundpost is thus both excited and radiates sound. Our experimental results make the hypothesis plausible, but show that body (global) modes play an important role too. In the range 500 to 600 Hz, a body mode,C3, constitutes a major part. TheC3 mode has a nodal line close to the normal soundpost position and is especially interesting as it seems to form a quality mark of a good violin.