Synthetic sounds are produced by electronic hardware or digital hardware simulations of oscillators and filters. Sound is created entirely from nothing using equations which express some functions of time and there need not be any other data. Synthesisers produce audio waveforms with dynamic shape, spectrum and amplitude characteristics. They may be generated for sounds corresponding to real instruments like brass or piano, or for completely imaginary ones. The combination of sequencers and synthesisers is mainly responsible for the genre of techno and dance music but can produce ambient backgrounds too. Synthesisers also play a non-musical role for creating sound effects like rain, wind, thunder or just about anything you care to imagine. The power of synthetic sound is that it is unlimited in potential, just as long as you know how to figure out the equations needed for a certain sound.