Physical modelling is a method of synthesis in which a mathematical model of the instrument being synthesized is used to create the sound. It is the best way of approximating a real instrument. A polyphonic synth can play several notes at the same time. The polyphony is the number of notes a synth can play at once. Most filters can emphasize the frequencies just before those that are reduced in volume.
Resonance is the degree of emphasis that occurs.
Allows a sequence of notes to be put together to make songs. See analog synthesis. Many analogue keyboards allow one oscillator to be synchronised to the other. This forces the waveform of the slave oscillator to restart whenever the waveform of the master oscillator restarts. If they are set at different pitches this means the slave oscillator will have its waveform chopped rather than cycling perfectly, giving the sound a hard edge.