New Free Synth Is ‘King Of FM’

Free Music Software: Audiokit developer Matthew Fetcher has introduced King Of FM, a free software synth for iOS and Mac that’s based on sounds of classic ’80s FM synths, including the Yamaha DX7, DX7II, TX81z, and SY77.


  • Based on Multi-sampled recordings of classic presets from original 80s FM synthesizers
  • Standalone iPhone/iPad app & iOS AUv3 Plugin
  • Use with a MIDI Keyboard or iOS DAW
  • Over 200+ Presets and over 10,000+ individual samples
  • FX: Phaser, Chorus, Reverb, Ping-pong delay, Crush, Stereo Fatten, and more
  • Over 2+ gigabytes of sounds compressed to under 400 mb
  • udio recording: record your sounds then export wav files
  • Use as an iOS Plug-in in hosts like GarageBand, AUM, Cubasis, Beatmaker 3, and more
  • Run on your silicon Mac (Standalone version)
  • Includes full lifetime license for both iPhone, iPad, and Silicon Mac

“We are all volunteers, we do not get paid anything to make this app,” notes Fetcher. “We would be humbled if you checked it out. 100% of any proceeds from other apps go to support the AudioKit open-source project.”

Pricing and Availability:

King Of FM is available now as as a free download.

31 thoughts on “New Free Synth Is ‘King Of FM’

  1. another player of samples of true FM synths… meh. If this was a true FM synth, and not a sample player, maybe it’d be interesting. samples of FM is akin to samples of a B3… an approximation lacking true expressiveness. just sayin’

    1. Well, not just any samples, but some of the finest DX7 samples in the world, as praised by major magazines, the Power DX7 channel, Sting’s producer, and even Herbie Hancock himself used our samples in this app (and he could use anything)! Heck, we’ve had producers say they’d happily shell out $99 just to snag these samples on their iPhone.

      As an experienced audio framework developer who has written code that powers hundreds of both what you might call “pure” synths and sample-based apps on the App Store, I can confidently state that most FM synths on the market, ranging from free offerings like Dexed to premium $100+ VSTs, utilize the same open-source 8-op DX7 FM generator code. This is a little-known fact (dirty little secret?) about FM VSTs and apps.

      What’s even more mind-blowing is that that exact 8-op code is being harnessed to train G****’s upcoming music creation AI system, and maybe even other AI systems, too. Fast forward to this time next year – music made with any VST FM Synth will end up sounding eerily similar to AI-generated playing.

      With this app, I’m on a mission to offer musicians a chance to craft unique and expressive sounds that’ll make them stand out from the AI-generated noise.

      If you’re seeking the same exclusive first-choice FM sounds used by some of the world’s top producers, this app’s got your back. And hey, if you decide to pass on it, no hard feelings; we don’t make a dime from it.

      At least with this app, musicians have a fighting chance of having expressive and real tone. And more importantly, not sounding like AI!

      Your friends at AudioKit

  2. I don’t really get the point here: it’s easy enough to emulate an FM synth, including the low clock speed used in the original DX7s, no need for samples, unless you really want to be faithful to lower quality D/A converters… odd.

    1. The “King of FM” refers to the SY77 portion of the app – this app is mostly SY77 sounds.
      Here’s a little something AnalogMatthew (head dev) wrote about the SY77. I’m sure it might spark some debate to what synth is the true “King of FM”



      The Yamaha SY77 is a legendary synthesizer from the golden age of synths, first unleashed upon the world in 1989. This little-known synthesizer kicked some serious ass in the world of FM synthesis, earning its title as the “King of FM.”

      Legendary musicians like Brian Eno, Vangelis, Tangerine Dream, Jean-Michel Jarre, and Vince Clarke couldn’t resist the allure of the SY series. They hopped on these synths and cranked out some of the most groundbreaking tunes of their time. Lost to history, it’s no exaggeration to say that the SY77 played a vital role in hundreds of artists’ musical success.

      Listen, the Yamaha SY series had a hell of a run…

      So, when I kicked off the King of FM project in 2020, I initially got my hands on an SY99. But it just didn’t have that raw, unfiltered magic I was looking for—it was too damn clean. I couldn’t bring myself to create an app if the tone wasn’t right, so I shelved the project for a bit.

      Then, I stumbled upon an SY77, and let me tell you, it had the sound I’d been searching for. I spent the next two years sampling the hell out of it, racking up probably 10+ gigabytes of SY77 samples on my hard drive (You might say I have a sampling problem).

      But I didn’t stop there. I painstakingly sifted through the samples and cherry-picked the top 100+ or so multi-sample sets—those with the most captivating character. In the end, this app boasts 2 gigs of SY77 samples, compressed into a sleek package weighing in at under 400 MB.

      And now, you can have these DX7 & SY77 sounds in the palm of your hand. Free forever


      1. I told my wife that there would negative comments about this and sure enough.

        It’s an awesome sound source, and it’s for FREE, geezus if you don’t need it or can’t appreciate the fact it is FREE…go make your own app and let the boo birds here chicken peck it like a bunch of naggy old ladies LOL

        Props to the developer for the civility and patience shown in the responses to the Karen comments. Cheers. And thanks for the app.

      2. Thanks for explaining the real thought process behind this app. Really great to know it’s a work of passion and sampling a particular synth for its imperfections. Thank you for all your time and hard work.

      3. Well now, even though I’m not a fan of sampled synths (much prefer the real deal) as the (former) product manager at Yamaha for both the SY77 and SY99, I must thank you for your kind and accurate words about both of “my” synths… those of us inside Yamaha at the time all felt the SY99 was what the SY77 should have been, but regardless, both of them are capable of an astounding range of tonalities, largely due to the inclusion of samples both as an independent sound source AND as a modulator into the AFM sound engines. In fact, the whole signal chain was pretty revolutionary for it’s time, we all considered it a powerful DSP engine rather than an synth voice w/efx hung on the back. I did 1:1 presentations of the SYs to musicians including Chick, Herbie, Donald Fagen, all of whom found it to be a solid and inspiring instrument. So kudos for heralding my old baby !! I guess I’ll have to give this a spin after all 🙂

        1. It is truly an honor to hear from you! It would be the greatest gift to hear what you think about the app—Perhaps we can even include something about you in the materials and/or further highlight your thoughts and amazing work! [email protected]

  3. Always a wank fest here. The app doesn’t so A B or C. They never actually critique the sound. “Does it sound good and fit the song you are working on” is all that matters. The rest is guys (yes, usually guys) complaining about some detail that doesn’t matter.

  4. i have a love hate relationship with audiokit apps. I love that they do so much for the community, with their open source, often free and cheap apps. They sound great too. However, i encounter so many bugs and crashes with them, ive stopped using them. At least on iOS. not sure about desktop.

      1. I’m glad you’ve taken that feedback seriously, I had a lot of crashes with the D1 synth and ended up requesting a refund.

  5. Why is this app “Standalone version” only on Mac? Rather pointless if one can’t use it as a plugin in Logic or Ableton Live…

      1. Not lazy-watched the video but, I don’t need to explain myself for the comment I’ve made – especially to you.
        It is NOT truly AU compatible with M based Mac – it requires a hack… according to video

    1. What more do you want for free?! j/k

      All jokes aside – You *can* use it as a plugin. It’ll run as a plug-in in Logic & GarageBand on your Mac Silicon. Though we’re not supporting it – can’t say how well it will work compared to a native plugin.

      If you watch some of the videos (like the one above) and the GarageBand Guide video, you can see it in action. Patrick from the GarageBand Guide has been using it as a Mac plugin without any problems.

      But…Your results may vary! 🙂

      1. OK, downloaded it on my iPad Pro and Mac mini m2-pro.
        Works as prescribed on iPad but got immediately isolated on Logic Pro.
        Also not recognised by Ableton Live Suite 11

  6. I’d prefer access to these sounds as Kontakt or soundfont presets instead of a separate standalone player app. Any cahnce of this? thanks!

  7. Try it out, it’s free. If you don’t like it you can always uninstall it. I like all the AudioKit stuff, this one is most like SagaSynth, just with a different sample set and a few different parameters swapped out. Overall I’d say it’s pretty rad and once it’s updated as a au3 it’ll be even better.

  8. I have to compliment the FX section. Even as over-used as some of the sounds might be, those will stretch the value of the library nicely. I was more of an SY85 man, but the total SY pedigree is pretty good. I banished FM over time, though, in favor of phase distortion and physical modeling. All the great bells, yet less brain-twisting.

  9. I have two previous AudioKit releases and they are both fun & intuitive. I have no idea why this one is getting so much ChadFlack. It’s free and it works and it looks great.

  10. This is a great tool…to add to my bag, to inspire…and its FREE! Thanks for that. Negative comments show a lack of understanding or maturity…it’s about creativity.. not always technical perfection…

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