The sound-producing component of a synthesizer is called the oscillator. The oscillator is capable of producing both frequency and harmonic content. This means that the oscillator can produce notes of a recognizable pitch and that the oscillator can impart to those notes a particular quality or timbre. This latter gives the synthesizer the capability to reproduce the characteristic complex waveforms associated with instruments such as pianos, violins, brass instruments, and so on.
The most basic waveform produced by oscillators is the sine wave, composed of only one specific frequency. Three other simple types of waveforms are the square, triangle, and sawtooth. Figure 1.12 shows all four of these.