This helicopter-ish sound began with a sound design session creating Neuro/ D 'n' B style basses. I accidentally played it a few octaves too low and realised it sounded like an exaggerated helicopter/ sci-fi engine sound. The sound itself was created using FM synthesis within Native Instruments FM8. I began as most sounds do with a simple sine wave pitched to a low octave. The gradual engine noise/ rotary blade sound evolved from subtle modulation of the frequency of the sine wave using varying amounts of de-tuned odd-shaped wave or formant generators, which interact with the frequency information of the lower sine wave to create a pulse of varying speeds according to the relative pitch of the sine. The other layers are simply modulated filtered noise being faded in and out throughout and a gradual falling-pitch sine wave to emulate the sound an engine makes as it passes by. Later processing included panning of each layer, volume automation and subtle reverb for added depth and realism. Please feel free to use this in your productions and leave a comment or message me for any more information or just to show me what you did with my sound! Enjoy! - Matt