Skip to content
blzr docs

Build: FM Voice

A two-operator FM synthesis voice. The modulator oscillator feeds into a multiply node that controls modulation index (depth), then into the carrier oscillator’s frequency input via an add node. Changing the modulator frequency and index creates rich harmonic and inharmonic spectra from just two oscillators.

Step 1: Add the modulator oscillator

Section titled “Step 1: Add the modulator oscillator”

The modulator generates a tone that will modulate the carrier’s frequency.

Nodes added: fm-mod

Step 2: Scale with modulation index

Section titled “Step 2: Scale with modulation index”

The mul node multiplies the modulator output by the index value — higher index means more harmonics.

Nodes added: fm-idx

Connections: 1 new

Step 3: Add carrier frequency offset

Section titled “Step 3: Add carrier frequency offset”

The add node shifts the modulation signal so it oscillates around the carrier’s base frequency.

Nodes added: fm-sum

Connections: 1 new

Step 4: Add the carrier oscillator

Section titled “Step 4: Add the carrier oscillator”

The carrier oscillator produces the audible output. Its frequency input receives the modulated signal.

Nodes added: fm-car

Connections: 1 new

Step 5: Add output gain

Section titled “Step 5: Add output gain”

An amp node at the end controls the voice’s output level.

Nodes added: fm-amp

Connections: 1 new

Step 6: Group into a module

Section titled “Step 6: Group into a module”

Select all five nodes and press g. Expose audio-out, and the carrier frequency, modulator frequency, index, and level as parameters.

What you just built

Section titled “What you just built”

A reusable FM Voice module with 4 exposed parameters and 1 exposed port.

Select it in the Module Library (SPC m) to add one to any patch.

Next steps

Section titled “Next steps”