4 operators

with individual envelopes, key scaling, and modulation sections

sound engines

8 Routings

derived from classic four operator FM synths

sound engines

3 Sound Engines

modelled on 1980s hardware units


8 Waveforms

derived from the Yamaha TX81Z



2x, 3x, and 4x — works in polyphonic mode



iPad only

with eight different temperaments



iPad only

tempo-syncable with up, down, up-down, and random patterns



Reason only

affects the pitch of each operator individually


Free of farty brass sounds

FM4 instantly self-terminates when exposed to a farty brass preset

FM4 for iPad

fm4 ipad

FM4 for iPad has reached #1 on the Appstore list of most popular music apps. It comes with a build in arpeggiator and is controllable via Core MIDI and MIDI over Bluetooth for integration in a studio environment or for live use with an external keyboard/controller. It supports Inter-App Audio and is compatible with Audiobus for easy integration with other apps.

FM4 for Reason

fm4 Reason
fm4 Reason back

FM4 for Reason is a newcomer in the Propellerhead Rack Store. It comes with numerous CV inputs/outputs for external control, including individual inputs for modulating both the level and the pitch of each of the four operators. A unique feature of FM4 for Reason is its drift knob for spicing up sounds with a more organic feel. FM4 is fully automatable and supports Remote.

Download on app store

Audio demos

Powerful sound with a modern interface

Modelled on the first commercially available FM synths from the 1980s, FM4 provides the same gritty sound, but with a modern interface, and without being bound by the limitations of the original units. For example we have redesigned the pitch envelope with a tweakable curve ideal for percussive sounds. Thus FM4 is capable of producing a multitude of sounds, ranging from punchy basses, crystal-clear bells, and lush pads, to organic textures, striking drums, and piercing leads.

Raw digital character

At the heart of FM4 is our digital FM modelling engine which has been carefully modelled on original hardware units from the popular DX series. Every aspect of the hardware — from envelope curves to sine-table sizes and quantisation errors to digital-to-analogue converters — has been meticulously analysed. With a combination of complex math and substantial hours of tweaking, we have committed ourselves to recreate that filthy, quirky sound of the original units.

FM synthesis made simple

Over time FM synthesis has garnered a reputation of being arcane and difficult to master. We think that this is not deserved. To warrant our claim we have given FM4 a carefully thought-out, stripped-down, yet powerfull, user interface. With every parameter being available on a single page, alike traditional analogue synthesisers, FM4 facilitates a workflow with minimal overhead, encourages exploration, and allows for faster programming yielding instant sonic results.

All product names used are trademarks of their respective owners, and reference to these here in no way constitutes an association or affiliation with Primal Audio. All trademarks are solely used to identify the products whose sound was studied during the development of FM4.