Effects are devices or algorithms which take an input signal and modify it producing an output signal. The output can be anything from subtly different to drastically different from the original.

The commonly used effects can usually be grouped by function as follows :

• Amplitude/volume modification
• Dynamics modification (compression, limiting etc)
• Filtering
• Waveform distortion
• Time delay based effects (echo, reverb etc)
• Pitch and time scale manipultaion