The overdrive effect is used to add harmonic distortion to a sound. This can be useful to make a sound bigger, brighter, grungier, or rougher. It is also a typical effect used on some musical instruments, especially guitars. Overdrive works by passing the sound through a non-linear distortion. For sounds that have only a single musical tone, this will add harmonic overtones to the sound. For sounds which are made up of more than a single tone this will also create non-harmonic intermodulation overtones which can sound vaguely metallic or bell-like.
The overdrive effect allows you to choose one of three possible types of distortion. The first, called soft-clip, will add a warm distortion. The medium curve distortion adds a slightly mode dramatic effect, and the hard clip adds a harsh buzzy sound.
For all of these distortion types the amount of distortion increases as the sound gets louder. The drive parameter allows you to boost or cut the level of the sound before the distortion to get the right amount of effect. The out_gain parameter is used to adjust the level after the distortion.
The overdrive effect also has a tone parameter which allows you to adjust the relative amount of high and low frequencies in the output of the effect.
2013/11/22 Initial version.