AddSynth is a graphical tool to easily generate sounds using an additive synthesis technique. It allows the user to explore harmonic or inharmonic sounds, and graphically edit some perceptual parameters such as pitch bend or amplitude envelope, add some partials, delete some harmonics, etc. This low level and analytical approach of the sound synthesis is an interesting way to understand the complexity of reproducing acoustic sounds. The program can save and load the created sounds into highly compressed proprietary files with no loss of quality.