IMFMSynth - 8 Operator FM Synth Interview

FM synth fans should find joy in the release of IMFM synth, a very reasonably-priced FM softsynth for Mac & Windows. A modest $19 intro price belies this instrument's scope & complexity; it contains 8 Operators, wavetable import, three filters & a wealth of other sound design options. I sat down with creator - Kaito Sato, to find out more.

Thanks for chatting to me about IMFMSynth, your new 8-operator FM soft synth for Win/Mac - tell me about the unique ideas, features and sound-creation possibilities your instrument brings to the synth world.

Thanks for taking an interest in IMFMSynth. There are two main ideas I'd like to highlight. The first is the routing interface. IMFMSynth keeps the traditional idea of FM operators, but instead of choosing from a set of fixed algorithms, you connect operators directly by dragging and dropping between them.

That idea was partly inspired by modular synthesizers. I wanted someone who is used to thinking in terms of "this oscillator modulates that oscillator" to be able to look at the screen and immediately understand the signal relationships.

The second idea is that a wavetable can itself be an FM operator. FM is extremely powerful, but for someone who is not already familiar
with it, I think it can be difficult to know where to begin. Many people may initially use FM only to add some extra harmonics to an attack, or associate it mainly with bells, electric pianos and other classic FM sounds. Modern musicians, on the other hand, are often already very comfortable creating the main character of a sound with a wavetable.

So I thought: why not let the wavetable handle most of the basic tone, and then use FM to shape the attack, texture and harmonic structure
around it?

That gives people a relatively simple entry point, but it also gives them a reason to become curious about FM itself. I'd love younger musicians to have their own version of that moment people once had when they first heard an FM electric piano and thought, "What on earth is making that sound?"

Of course, once you go deeper, the eight freely routable operators allow much more complex structures. A wavetable can be a carrier, a modulator, or part of a much larger FM graph. IMFMSynth can also import DX7 SysEx patches, so classic FM sounds can become a starting point for something much more modern.

Wow, yes I agree - wavetables can be a great entry point into modern FM sound design. Please tell us a little about your background -- I read on your profile that you studied science, how did you get into synthesizer creation?

There are probably three parts of my background that came together here.

First, I graduated from Ichinoseki Kosen, which is part of a type of technical college system that is fairly unique to Japan. Kosen education is strongly focused not only on theory, but on training engineers who can actually build things and apply technology in the real world. It was a very natural environment for the idea that if there is something you want, one of the first things you should consider is simply trying to build it yourself.

Later, at Niigata University, I studied mathematics, particularly analysis. Because I came into pure mathematics with an engineering background, I was always interested not only in abstract mathematical objects themselves, but also in questions such as how they can be approximated and calculated efficiently on a computer.

That combination has been very useful for synthesizer development, because real-time DSP often depends on performing large numbers of mathematical operations very quickly. As a result of that interest, I also maintain an open-source library of mathematical functions optimized for DSP:

https://github.com/skpub/DSPmath

There is also a musical side to the story. My grandfather taught traditional Japanese folk music, and my parents have been playing in bands for more than forty years, so music was always around me while I was growing up.

I think synthesizer development is where those three things eventually met: a culture of building things yourself, an interest in mathematics, and growing up around music.

Fascinating, talking of different worlds meeting - FM with wavetables definitely opens things up compared to old-school "sine wave FM". How does IMFMSynth handle wavetables, can you import your own?

In IMFMSynth, I deliberately treat a wavetable as simply another waveform that an operator can use. From the user's point of view, it sits alongside sine, triangle, square, saw and various types of noise. I wanted to avoid making wavetable synthesis feel like a completely separate synthesis engine that the user has to learn.

So for someone already familiar with a traditional FM synth, the mental overhead is basically just: "this operator has more waveform choices now."

Yes, users can import their own WAV files, and they can also draw waveforms directly inside IMFMSynth. There is some engineering behind that simplicity. When the user creates or edits waveform data, IMFMSynth prepares the necessary wavetable representation in advance, so the synth does not need to repeatedly perform expensive waveform-generation work during playback.

I care a lot about this kind of optimization. A synthesizer can have very sophisticated features, but if it consumes too much CPU to be practical in a real project, musicians eventually stop using it. For me, real-time performance is part of the instrument design, not something separate from it.

Completely agreed - soft synths need to run on vastly differing setups, after all! By the way, IMFMSynth is available in multiple languages - how important to you was it that the synth should have Japanese language support?

It was quite important. Japan still has a very large, relatively self-contained Japanese-language market and musical culture, and there are many users who are not comfortable working entirely in English, especially among older age groups.

At the same time, a large proportion of music software is still English-only.

Since IMFMSynth is being developed in Japan, I felt that providing a synthesizer that Japanese users could understand and trust in their
own language had real value. I see localization as more than simply translating labels. It is part of making the product approachable to a particular market.

Once the software architecture supports localization properly, adding further languages also becomes much easier. IMFMSynth currently supports nine languages, and I would like to expand that further in the future.

Incredible work. Were there any major challenges along the way when creating IMFMSynth?

One major challenge was gathering the knowledge that I personally lacked. I'm an engineer with a background in software and mathematics, but I don't consider myself an expert in every aspect of modern music-production workflow.

So rather than assuming that I know what musicians want, I've been going directly into user communities, asking what people actually need, implementing ideas, and then seeing how people respond. Another major challenge is balancing complexity with usability. Technically, it is possible to keep adding more operators, modulation, routing, filters, effects and other features. But at some point, adding more possibilities simply makes an instrument harder to use.

For me, the difficult question is often not "Can I implement this?" but rather "Can I integrate this in a way that still feels intuitive and enjoyable?"

IMFMSynth is also not the first synthesizer I've attempted to build. I've written synthesizers several times before, including long before AI-assisted development was common, and I failed many times. Those failures were useful. I think IMFMSynth is the first one where all of that experience has finally come together into something that people I've never met are willing to spend money on and use in their own music.

That makes it especially rewarding to see people from different countries buying it and sending me detailed feedback.

How much is IMFMSynth and where can our readers download a copy?

IMFMSynth is currently available at a beta promotional price of $19 / ¥3,000.

My long-term target for the regular price is around $49 / ¥7,500, but I do not plan to jump directly from the current price to that level. A major update and a set of factory presets are currently in development, and once those are ready, I expect to raise the price by one step. Any price increase will be announced on the official website at least one week in advance.

IMFMSynth can be purchased directly from:

https://imfm-synth.com/

It is available as VST3 and CLAP on Windows, and VST3, AU and CLAP on macOS.

There is also a browser version on the website using the actual IMFMSynth DSP compiled to WebAssembly, so readers can try the instrument and hear what it does without installing anything first.

Thanks for chatting to us, and good luck with the IMFMSynth project!

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