Primal Audio FM4 Synthesizer Promises To ‘Reinvent FM Synthesis’


FM synthesizers have a reputation for being powerful, but painful to patch.

Primal Audio today released FM4, a new FM synthesizer for iPad they say reinvents FM synthesis, making it more accessible and intuitive.

FM4 is a four operator FM synthesizer for iPad. FM4 is modeled on Yamaha DX synths of the 80s, but with a modern interface and free of some of the limitations of the original synths’ technology.

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.

According to Primal Audio, every aspect of the hardware — from envelope curves to sine-table sizes and quantization errors to digital-to-analogue converters — has been meticulously analyzed, in order to recreate the sound of the original units.

The interface of FM4 is much more intuitive than the original, putting every parameter on a single page. No menus, tabs, or jumping from page to page.


  • Four operators configurable in eight different routings
  • Three sound engines modelled on 1980s hardware units
  • Eight waveforms derived from classic FM synths
  • 2x, 3x, and 4x polyphonic unison
  • Tempo-syncable arpeggiator with up, down, up-down, and random patterns
  • Microtuning with eight different temperaments
  • Supports Inter-App Audio, background audio, and support for Audiobus is coming)
  • Up to 24 voices of polyphony
  • Presets can be imported/exported through iTunes

Note: MIDI is not working in the initial release. The developers say that an updated FM4 that adds MIDI support has already been submitted to Apple for review.

Here are official audio demos:

The developers have created an FM ‘manifesto’ to challenge people’s ‘misconceptions’ about FM synthesis:

FM Manifesto

1) FM synthesis is unintuitive and incomprehensible.

Due to a combination of cumbersome interfaces, poor terminology, and plain calumny, FM synthesis has over time garnered a reputation of being arcane and hard to grasp.

We have put great effort into giving FM4 the most simple conceivable, yet powerfull, interface — with every parameter being available on a single page — akin to early analogue synthesizers.

2) FM synthesizers sounds cheesy and farty.

When the first FM hardware synths came out, only a few people embraced their underlying concept and undertook programming them. Instead they were primarily used for their, at that time enticing, factory presets and commercially programmed banks.

oday FM is still being identified with cheesy electric pianos and farty brass sounds. To put an end to this FM4 does purposely not include a sysex converter.

3) Software FM synthesizers sounds clean and sterile compared to original vintage FM hardware.

Contemporary implementations of FM synthesis typically focus on reducing aliasing and related digital artifacts resulting in a sterile and lifeless sound.

With FM4 we have taken the opposite approach and analysed and incorporated inherent sonic aspects of original 1980s hardware units, such as the bit-depth of internal sine-tables, quantisation errors, and digital-to-analogue converters.


It is time to reinvent FM and we encourage musicians to dive into and embrace what was formerly considered as /the black art of FM programming/.

FM4 is available now in the App Store for $0.99, through the end of December.

If you’ve tried FM4, let us know what you think of it!

41 thoughts on “Primal Audio FM4 Synthesizer Promises To ‘Reinvent FM Synthesis’

  1. Badass on every level. Has a quality grit one would appreciate from hardware. Really makes FM comprehensible, though I think I’m still a ways away from programming with exact vision! This makes the perfect learning tool as well as a great instrument, something that Tf7 and DXi were lacking on. Really looking forward to putting all newfound knowledge towards my actual Dx7, and putting TF4 next to it too!

    1. What the feck can you get for £0.69 … a chocolate bar if you’re lucky! Maybe a couple of packets of rizla, or a piece of fruit, certainly not a coffee, a bus ride or anything more substantial to eat… it does’t go very far at all these days!

      But wait… you can have this seriously awesome 4op FM synth… o_O

        1. Dexed is nice. This is also a nice replacement for my former DX100 (R.I.P.) / 27 / 21, or more accurately, a DX11 (which I never got to see).

      1. Yeah, so they promise MIDI instead for the very next release and in the meantime charge us 99 cents. That sucks. How am I going to afford to buy my third of a cup of coffee now? 🙁

  2. I do own probably most if not all FM based iOS synths, but this one takes the cake 🙂
    BTW; Why is it that the patch from TX-81Z called “Lately” (4 op bass synth patch), is never featured in all of them..? 🙁

      1. As a programmer, I imagine there’s a bit of work adapting to the “connections” for iOS “audiobus” and the VST interface (even if its OSX only). But I don’t do sound programming.

  3. This one is very powerful. I really appreciate that tuning system is switchable. About no midi – i was able to connect lemur for sending notes. Waiting for audiobus support..

  4. I was hoping to have some effects, such as delay, chorus, reverb, or even a juicy filter. Guess you can only get so much for a buck these days. Other than that, no complaints. I do notice getting it to pull off some of the extreme sounds of my DX200 doesn’t seem FM4’s forte as such. But again, maybe that’s just as well.

    1. 2 years later, you can. Use camera kit with USB midi controller, works fine. I love playing with this little guy (even for a whopping $7), since my DX100 died a while back (no luck on battery soldering).

  5. they’re reinventing FM by meticulously analysing and recreating 80s units. hmmmm

    self-contradictory hyperbole aside, this thing sounds really great and is super easy to tweak, and they’ve promised midi / iaa / audiobus very soon.

  6. The only other FM synth that makes FM fun and experimental is Yamaha’s DX200 (FS1r is stunning too, but complicated without a connected software interface). You cannot go wrong for this price!

  7. I would love a Rack Extension version of this for Reason. I know we have the PX7 but variety is good. Sound damn good in those demos. I would happily pay $99 for an RE version.

  8. Wot no midi? Wot no audiobus?

    Only joking! This is very very potent and a steal at 69p. Bloody hell, it sounds great, easy to use, simple but gorgeous design and stable to boot!

    The dev has done a great job here. Also not a big fan of FM, but I can certainly get some great patches out of this beast.

    Easily the best deal of 2014 in the iOS world without a doubt!

    How he can afford to flog this for 69p is beyond me?!?!!

  9. Grabbed the app as soon as I saw this post. It’s fantastic! I hadn’t really delved into FM before, but this app is a joy to work with. Latch a random arp, play a big chord, and start tweaking! Haven’t had this much fun exploring a synth app since Nave came out.

  10. Super fun to play with, and sounds fantastic. Can’t wait for the Audiobus and MIDI implementations so I can start putting this into everything!

    Great job Primal Audio!

  11. Seeing as it is a 4 operator synth, it would be great if I could create patches on it and load them into my TX81z. Perhaps in future updates? This synth looks to be what the DX200 was going for but failed. I tried to embrace the DX200, but despite having a cluster of knobs it still required a software editor to get into the real nitty gritty. Plus the all important main parameter knob had a reputation for flaking out, which was distressful when trying to create a patch.

  12. Insta-purchase but I disagree with the decision to not include sysex import. So many great basses, bells, pianos and organs in my sysex collection :o(

    1. Not sure sysex import would would very well. Looks like the envelopes are ADSR, which is fine), but don’t Yamaha’s have more complicated envelope controls?

      As soon as you do SYSEX on an FM synth, you get a forum full of people who claim your synth doesn’t sound like the original, or people who suddenly want you to be able to import that huge collection of Sega Genesis instruments ripped from all the game carts.

      I guess I sympathize with the developer on this issue. 🙂

      1. Sorry, I meant “would work” not “would would.” I’d PAY for an edit button here, just so I could avoid looking like an idiot once a week.

  13. MIDI (note) support arrived today. Sustain pedal doesn’t work, but pictch bend and modwheel (-> LFO itensity) do.

    I noticed some latency too, but not too high to hinder performance, IMHO.

    BTW, works perfectly here on iOS 7, even on an iPad 2. Even though, when you use unison modes, and all operators, polyphony gets eaten up quickly.

  14. Downloaded but it’s not working for me either on iOS 7.0.4. It crashes as soon as I launch the app.

    Edit: Just saw this is mentioned on the app store description:

    “DISCLAIMER: Crashes after startup on iOS 7.0.4. Works fine on iOS 7.1 an upwards. The cause of the crash is a bug in Apples most recent version of its app development tool. We are looking into this and will issue an update as soon as possible.”

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