The shakuhachi, a Japanese flute, is a rather small instrument with a simple geometry. Still, it appears to have a complicated spatial sound radiation characteristic. This effect results from interference of sound emanating from finger holes and the blowing hole as well as diffraction around and acoustic shadow behind the instrumentalist. Even in absence of room reflections, the pure direct sound of musical instruments already creates the impression of a certain extent of the source. This perceived extent is especially large for listeners close to the instrument and decreases with distance. This effect is investigated in more detail on the shakuhachi. The sound of a shakuhachi is recorded in an anechoic chamber by a circular microphone array consisting of 128 microphones. Amplitude and phase per frequency and angle around the instrument are measured. Interaural phase- and amplitude differences as well as the correlation of the signals arriving at the two ears are calculated for several listening positions at various angles and distances. These parameters are compared between different playing techniques. It is discussed how far the parameters are suitable to explain the perception of the spatial source extent.