additive synthesis
Articles about additive synthesis:

Torley is back in action with another Project Preset video, a series of videos in which he explores the presets of new software synths.
This time, Torley takes on Native Instruments Razor.
Razor is a new software additive synthesizer that runs in Native Instruments Reaktor. Read more…

This video takes a look at additive synthesis in Native Instruments’ Reaktor:
Native Instruments have just launched their latest Reaktor Synth, called Razor, and it is causing quite a stir in the sound design and production communities.
So what makes this synth so exciting? Well it is down to a process called additive synthesis.
Put in the plainest terms possible, additive synthesis is the summation of simple tones to create more complex ones. The sound is constructed from partials (or frequency components) firing in parallel, changing amplitude and even frequency over time.
Additive synthesis is a very powerful sound design tool because the many micro-variations in the frequency and amplitude of individual partials mirrors those that makes natural sounds so rich and lively, and the resulting sound remains clear and precise at all times, even when heavily modulated.