FM synthesis builds harmonic complexity up from sine waves; subtractive removes harmonics from a rich source

The two foundational synthesis philosophies differ in direction. Subtractive synthesis starts with a harmonically complex waveform (sawtooth, pulse, noise) and sculpts it with filters — removing partials to shape the timbre. FM synthesis starts with simple sine waves and modulates their frequency to generate new harmonics; the Yamaha DX7 used this approach and had no classic synthesizer filter “because it built the harmonic complexity up from sine wave modulation.” Recognising this distinction helps learners choose the right engine for a desired sound and avoid confusion when a synth has no filter section.

Examples

A sawtooth → low-pass filter chain is subtractive. A sine oscillator whose frequency is modulated by another sine (operator patching) is FM. The same brass-like tone can be reached by different paths.

Assessment

Given a synthesizer that has no filter section, which synthesis paradigm is it most likely using and why? Describe one sound that is easier to achieve with FM than subtractive synthesis.