Typically, oscillators allow selectable waveshapes to generate specific signal types based on sonic desirability. Different shapes have different sound signatures based on the harmonic series they represent on the frequency spectrum.
The list of basic waveshapes are as follows;
Depending in the wave shape itself, a combination of harmonic frequencies are generated providing a specific quality in the sound itself. In general, the more ‘smooth’ a waveshape is the less harmonic frequencies generated. Conversely, the more ‘rigid’ a waveshape is, the more harmonic frequencies are generated.
Let’s take a look at a pure, smooth sine wave shape @ 100Hz:
A sine wave is also known as a pure tone wave due to its lack of harmonic content. A sine wave produces one singular frequency based on the pitch of the oscillator or note generated.
Now let's look at a sawtooth wave shape @ 100Hz:
A sawtooth generates harmonic frequencies all the way up the frequency spectrum based on the fundamental frequency.
Waveshapes are the basis of particular sound signatures, and understanding the difference in character between various waveshapes will help with detection and aid in accurate sound design decisions.
For some synthesizers, waveshapes may be manipulated via various parameters and routing capabilities within the synthesizer itself.
Some synthesizers allow for FM routing. In this particular case, a waveshape can be distorted via frequency modulation which inherently applies harmonic content based on the frequency used to modulate the original waveshape.
Due to the 'sharpness' of a sawtooth wave, this waveshape is harmonically rich, therefore applying a LPF will help attenuate these bright frequencies and can create warm, full and powerful bass instruments. Simply using a filter this was will alter the waveshape itself due to the harmonic content being filtered out. A sawtooth wave would look a lot more smoother like a soft triangle wave.
Wavetable synthesizers allow waveshapes to evolve over time producing a lot of movement with just a singular oscillator. In other words, you are able to morph between one waveshape and another. When this method of synthesis is combined with traditional synthesizer functionalities, the most unique textures are produced.
Customized waveshape may be created by generating specific harmonic frequencies via a harmonic generator. These harmonics that are created will ‘distort’ the waveshape with varying degrees depending on the harmonic that is created.
The waveshape used in a synthesizer will determine how it can be manipulated via other synthesizer functions or post processing. A lack of harmonic content will provide a far less flexibile sound due to the lack of content involved. Harmonically rich waveshapes offer far more flexibility due to the abundance of information that is able to be processed.