Disclosed herein is a sound synthesis system for generating a user defined synthesised sound effect, the system comprising: a receiver of user defined inputs for defining a sound effect; a generator of control parameters in dependence on the received user defined inputs; a plurality of sound effect objects, wherein each sound effect object is arranged to generate a different class of sound and each sound effect object comprises a sound synthesis model arranged to generate a sound in dependence on one or more of the control parameters; a plurality of audio effect objects, wherein each audio effect object is arranged to receive a sound from one or more sound effect objects and/or one or more other audio effect objects, process the received sound in dependence on one or more of the control parameters and output the processed sound; a scene creation function arranged to receive sound output from one or more sound effect objects and/or audio effect objects and to generate a synthesised sound effect in dependence on the received sound; and an audio routing function arranged to determine the arrangement of audio effect objects, sound effect objects and scene creation function such that one or more sounds received by the scene creation function are dependent on the audio routing function; wherein the determined arrangement of audio effect objects, sound effect objects and the scene creation function by the audio routing function is dependent on the user defined inputs.