What part of an open organ pipe emits most of the sound and what is the spatial sound distribution for the harmonic tones? The sound intensity from a blown open organ pipe, tuned to C4 at 260 Hz, is measured in an anechoic room using a 3D sound intensity probe. The measurements are performed both in the vertical and in the horizontal plane in front of the pipe. The two dimensional sound intensity vector field for different harmonic tones are studied. The study focuses on the active mean intensity field and the results point out the main sources of acoustic power and their contribution to the far field. Pipes made of different material and tooled in different ways are compared. Interference phenomena between sources are also visualised. First it can be noted that the top and the mouth are the main sound radiators compared to the walls. They are of about the same strength for the first four harmonics. For the fifth and sixth harmonics the top is the main sound radiator. For odd numbered harmonic tones the mouth and the top emit sound in phase and for even numbers, out of phase. The material choice and tooling method affect the sound spectra.