Base class for all other oscillators.
This is just use for data type, so that can contain all subclass of oscilltors. Instance of Oscillator class have nothing to do.
example
Oscillator osc;
Oscillator[] osc_array = new Oscillator[3];
osc_array = { new OscSin(100,100), new OscCos(50,13), new OscTriangle(15,15)}
osc = new OscComposite( osc_array );