Frap Tools should be a well-known name to those in the Eurorack modular synthesizer world. In the past several years, this small Italian instrument design company has developed a reputation for being one of the premier developers of new instruments for the creation of electronic music.

They are one of the small handful of Eurorack modular synthesizer designers who have taken strides toward producing a thorough, complete complement of modules. Beyond simply "covering all of the bases" though, there's a different ethos at work behind their growing lineup: Frap Tools's modules collectively form a powerful, no-compromises, great-sounding, and inspiring musical instrument. There is a striking and remarkably well-thought-out consistency about their designs, and in my mind, the Frap Tools lineup feels less like a collection of modules, and more like a complete and very carefully considered instrument ecosystem.

But, Frap Tools is, in our eyes, more than just a gear company. More so than many manufacturers, they've cultivated a rich and fascinating culture around their instruments. From their active Discord community to their own educational efforts, they engage deeply and attentively with their user base—building a co-creative and downright exciting experience for anyone who decides to step into the Frap Tools universe. Education is central to their own public presence (see their YouTube channel or their ever-growing, consolidated user manual if you need proof), but they're unpretentious, inviting, and fun—encouraging a smart, exploratory, personal, and curiosity-driven approach to music and sound design.

In late 2023, we had the opportunity to sit down with Frap Tools founder/product designer Simone Fabbri and content manager Giovanni Grandi. We talked about all aspects of their company—their evolution, their design process, their approach to documentation and education, and the philosophical considerations behind their highly specific approach to user interface design. And of course, we talked at length about their most recent module, the quad filter/"sound seasoning" module Cunsa. What we got was an absolute masterclass in the concepts that go into developing a complete, unique musical instrument. Read on to see what they had to say.

An Interview with Frap Tools

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[Above: a Frap Tools system; image via Frap Tools YouTube channel.]

Perfect Circuit: Thanks for taking the time to talk with us! We want to get to some specific questions about your newest module, Cunsa—but since we haven't had an opportunity to interview you before, we'd like to start with some background questions about who you are, and what you do. So, we're curious—how did Frap Tools as a company come to be?

Simone Fabbri: The company came to life almost by accident, thanks to my background as a musician on one hand, and as a mechanical expert on the other. I came to Eurorack after many years playing saxophone and bass, and the mechanical side took over when I couldn’t find a modular synth case that could fold patched and had no visible screws—so I made myself one that could satisfy my picky taste. It was 2014, and that year I found that there was a space for small manufacturers to show their stuff at the NAMM convention in Anaheim. To attend the show I needed a company, so in a few hours I purchased the domain frap.tools, sketched the logo, and decided the name of the case, which then became the UNO. I remember that the original prototype, still visible on some media coverage, was 85 hp!

During the following year I met Federico [Foglia] and Antonio [Masiero], and thanks to their electronic skills I was finally able to start designing modules. As Frap Tools began getting an identity, Giovanni [Grandi] came on board to help us define our guidelines and communication, both among ourselves and to the outside world.

All of us have diverse musical and cultural backgrounds, and I think that this is what allows us to always have fresh perspective on our projects.

PC: We'd like to reflect on your first offerings as a company. Many modular companies take their first steps by offering what we think of as "centerpiece" modules: elaborate sound sources or audio processors are a really common starting point. But you folks didn't do that at all—you started with a case and some other offerings on the more "utility" end of the spectrum. Why did you start with these products specifically?

SF: In retrospect, I couldn’t have started anywhere else than from cases because I still don't have enough electronic skills to design a whole module on my own. However, when Antonio and Federico joined me, we decided that our first electronic product should have been a mixer, because it’s the bottleneck of every system. You can have the most exciting voices ever, but if you patch them through a mediocre summing stage, you won’t be able to experience it in full. Modules like oscillators or filters are indeed the most noticeable audio trademark of an instrument manufacturer, but we preferred to delay them until we felt mature enough. The market is already full of excellent oscillators and filters, and we released ours when we felt like we could provide a valuable contribution.

Giovanni Grandi: We can say that we wanted to prepare the ground before getting to the “centerpiece” modules, as you say. After all, a “centerpiece” needs to be the “center” of something, right? We wanted to create that “something” first, to provide a proper context for a Frap sound to express its full potential.

PC: So when you started the company, did you have a roadmap in place for the sort of system/instrument(s) that you wanted to wind up making?

GG: No, we didn’t. We have always been so focused on the next product in line that it would be false to state that we had a long-term roadmap. Even now, we have an idea of what can be added to the system and we carry on different projects, but none has a clear priority over the others—it’s all very natural and spontaneous.

PC: So, then, if you had to characterize the Frap Tools "system" in a sentence, how would you explain it? What are its strengths, its unifying design principles?

SF: It is a musical instrument meant to be practiced and played.

[Above: official Frap Tools video demo of Brenso, their Buchla 259-inspired oscillator.]

PC: It's difficult to ignore the influence of Donald Buchla on your work. Many of your modules—Sapèl, Fumana, Falistri, Brenso, Usta, and to an extent, Cunsa—seem to make obvious reference to specific modules or design concepts from his 200 or 200e Series. Needless to say, we're big fans of his work, and we're always interested to see how his influence manifests in current designs. What is it about Buchla's instruments or design philosophy that speaks to you?

SF: I personally love Don Buchla’s 4U format, the interfaces, and the ergonomics. I especially love that he chose to link the inputs and the knobs through arrows and arrange them in topologies that reflected the musician’s actions, rather than relying just on labels. A great example of this approach is the 292 module.

However, sometimes people like to compare our modules to Serge’s designs: less labels, more symbols, and denser modules. To some extent, I agree also on this.

GG: I also appreciate the fact that while all synthesizers are devices to create new sounds, Buchla’s instruments were also meant to create a new music, showing the distinction that later Rob Hordijk would make between “electronic instruments” and “electronic music instruments.”

PC: That's an excellent point—there can be a sort of conceptual difference between instruments that happen to involve electronics, vs. instruments that were designed specifically to make electronic music. I like that distinction.

So, returning to Buchla—I find it interesting (and important to note) that none of your modules are direct clones/translations of his original designs. In my opinion, you do an great job of using his concepts as a starting point, and then extending them to add new features, or to accommodate new potential workflows. Can you think of any specific examples where you feel like your additions to the basic concept have deeply changed the device's identity or artistic potential?

SF: Probably the closest modules to Buchla designs are Brenso and Fumana. Brenso fits in the tradition of complex waveform generators that traces back to the 259, but apart from the concept of two oscillators modulating each other with a waveshaping section, its application is completely different. It has through-zero FM, two wave shapers, and an amplitude/ring modulation section separate from the wavefolder. We spent a lot of time thinking about the semi-normalled connections and expanding the modulation with a CV input per every parameter.

With Fumana (whose ancestor is the 296) we tuned the bands differently and expanded the concept of spectral transferring, adding a dedicated array of 16 more bandpass filters. These features allow to use it as a 16-on-16 spectral processor that could accept also drums as its modulating signal. That seems a very natural improvement from the original 296.

GG: Sometimes a classic instrument design becomes an "archetype," something that is so embodied in the synth culture that cannot be ignored. I don't think that a good design must be "new" or "groundbreaking" at all costs; instead, I think that a good design should consider the history of the product and then carefully choose which elements to keep and which to change.

PC: Do the basic ideas for new Frap Tools instruments tend to originate from one person within the company, or is there a team of people who bounce ideas around when considering new products?

SF: As the company grows in people and awareness, we tend to be all equally involved in all the design stages. Of course I'm the one that makes the final decisions at the end of the day, but our approach is more "horizontal" now than it was at the beginning.

PC: I suppose that leads into something else we wanted to talk about: your design process in general. Can you walk us through the typical development process for a product, if there is a typical workflow? How do ideas evolve from an initial concept to a completed device?

SF: We follow an iterative design process, but its stages depend on the module. For a complex module, we start from an abstract concept and try to give it a possible physical shape (form factor, layout mockup, mechanical spacing and price range). Then, we design its schematic, make a board prototype, and test it. When the board prototype is stable, we design the PCB layout and make an actual module prototype.

We might go back to the previous stages and repeat the process a few times before closing the project and starting the production. Sometimes the cycle goes back to the PCB design, sometimes to the circuit design itself, and sometimes even to the interface design, like we're doing now for a new module that we plan to release in 2024.

For smaller and more straightforward modules, we may skip the board prototype and go straight to a module-like testing unit; and for larger projects we may spend more time in the concept stage. I remember that when we were sketching the concept of Fumana I made a rough simulation on Max, and the same I did for Sapel and Falistri. Brenso, on the other hand, needed many years in the graphic mock-up stage before starting the circuit design.

PC: So, I do have some other general questions I want to talk about, but let's talk about Cunsa directly for a bit. I suppose the biggest thing that strikes me about it is that, Fumana aside, it's really your first filter module. It never felt to me like your system was particularly missing a filter—and maybe this is a bit of a generalization—but I feel like most synthesizer companies probably would've released a filter design earlier in their journey. I suppose my question is this: how long has Cunsa been in the works, and why was now the right time to add a filter to your lineup?

SF: Designing a filter is something that must be approached very carefully: there are hundreds of filters out there, and most of them are iconic and sound good. So, we had to be really sure that what we were about to release could have been a valuable contribution to the sound design world, rather than just a redundant filter design with Frap Tools’ name on it.

Practically speaking, it took around three years—so not that much, considering there are older modules we are working on and are yet to be released.

GG: Filters are probably the section of modular synthesizers that can provide the biggest sound changes with the smallest "switching cost," meaning that swapping a filter is easy and doesn’t require too much of a workflow change for a musician. Maybe [this is the reason that there are] so many of them: they are easy to buy and easy to sell, like trading cards.

One of the reasons behind Cunsa’s large format design is that it sort of discourages the casual buy and encourages a more thoughtful approach from musicians.

[Above: a few of Cunsa's earliest proposed designs—note how the core functions seem to remain mostly the same, while grouping and placement of controls gradually evolves. Images via Frap Tools.]

PC: What was the initial idea that led to Cunsa? Was it inspired by anything else before it, in particular? Given the Buchla influence in some of your other work, I could see it maybe being like, a super expanded take on a quad LPG...or is that entirely wrong? And just...why put four filters in a single module?

SF: In my head it is an extension and a different take on the 291 [Dual Voltage Controlled Filter], but what you’re saying is not wrong at all. To be fair, the LPG behavior is quite marginal in the bigger picture of Cunsa’s design. The idea of making a quadruple filter didn’t germinate out of a clear predecessor, even though we had to confront ourselves with what came before us in the quad filter design category, like the Buchla 292 or the Cwejman QMMF.

GG: Besides being both quad filters, the 292 and the QMMF differ under many aspects. From my point of view, the 292 has more of a juxtaposed approach: it has four distinct filters that don’t talk with each other except for the final summing stage, and it encourages the user to use it to process four sources and maybe mix them. The QMMF, on the other hand, has four filters that can work over the same signal, so it can become a complex sound shaping device: its filters are compound, not juxtaposed. With Cunsa, we wanted to follow both approaches—or none, depending on how you see it—but with the compound aspect prevailing.

PC: So, looking at an individual channel of Cunsa—the controls are fairly straightforward. You've got cutoff frequency, separate outputs per filter type, Q (into self-oscillation), input gain, 1V/octave inputs...what do you find particularly special about the behavior of individual channels on Cunsa?

SF: We wanted to develop something unique but not different for the sake of being different from other excellent-sounding filters. The only idea we were sure about was that it had to retain the bass content at high Q settings: the rest was open to exploration.

While we were researching on the saturation quality, we had a flying pot that defined the filter's response to signal overload. We couldn't decide which one was the best, so instead of picking an arbitrary value, we chose to keep the pot and make it a user-definable parameter.

GG: So, we can say that the most unique control of the Cunsa was discovered by accident. We know that if a module has too many user-definable parameters it can become confusing to use and counterintuitive, but we think that in this case the Character knob really makes sense in the user experience.

PC: We think Cunsa is particularly interesting because, while at its core, it might just look like four filters, something about they way they're parameterized and the way the controls are group seems to suggest many potential uses outside the realm of simple filtering alone. Do you have any particular favorite patches with Cunsa, other than just using it like a typical filter?

SF: That’s correct, we wanted to create a module that could take the shape of its users’ workflow.

GG: We can say that Cunsa is a protean module, and through the semi-normalled connection it can become anything between a saturation unit and four oscillators. A couple of our favorite patches are the phaser and the partial oscillator.

If we set the four filters to lowpass, bandpass, bandpass, and highpass, gently spread their cutoff frequencies, and modulate them with the same LFO though the semi-normalled V/oct input, we can obtain a sort of phaser.

If we crank the Character and Q knob all the way up we make the filters self-oscillate and we obtain four sine wave oscillators with very good tracking. We can use them individually, or take advantage of the semi-normalled V/oct input to play them at once. They can become four partials of an oscillator (of course without phase control) and we can tune them to harmonic intervals or to inharmonic ones to create complex timbres. And if we turn the Q knob down just below the self-oscillation point, we can use a trigger signal into the audio input to ring the filters and obtain a very organic plucked sound.

But the coolest patch is the one yet to be discovered (let’s pay a sort of tribute to Enzo Ferrari), so we’re very excited to hear some demos by the users!

[Above: some of Cunsa's final design iterations—ending with the final product design. Images via Frap Tools.]

PC: We talked earlier about the fact that some of the earliest Frap Tools products were more utility-focused than some recent releases. Do feel that Cunsa's design was significantly affected by your work on previous more utility-focused products?

SF: I wouldn’t have thought about that in those terms, but I must say that you are right. A module like the 333 is emblematic because at its core is “just” a buffered multiple and a DC-coupled summing stage. However, the semi-normalled connections allow to use its three sections independently as mixers or multiples for audio or CV or together as a 1-to-9 multiple or 7-to-1 mixer, and anything in between.

This flexible approach is what allowed us to pin the unique character of modules like Brenso or Cunsa. Modules like the 333 and 321 were launched together with modules like Sapel and Fumana—they were a useful addition to the system in these days, so I’d say that we may have a utility modules proposal (with numbers as names) and deeper ones with (acronyms and dialect names). This also mean that we’ll probably have utility modules also in the future.

PC: Returning to more general questions—the design of your modules is quite striking. Of course, one of the most obvious things to point out is the almost complete lack of text-based labels; instead, you seem to rely on color-coding, simple symbols, and lines to help the panel suggest how a device works. How did you settle on this approach?

GG: Ferdinand de Saussure, the father of modern linguistics, said that the two main features of a verbal language are arbitrariness and linearity. Arbitrariness, because the meaning of the words is not in the words themselves, but it is assigned to them through use. Linearity, because we can't process or speak two sentences at the same time.

Other non-verbal languages aren't linear and allow more pieces of information to be processed simultaneously. For example, road signs can be combined to deliver different messages, and we can process them at once in the blink of an eye.

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[Above: the Frap Tools module Falistri—a great example of their graphical language.]

With our design, we're trying to develop a consistent nonverbal interface language, driven by a single question: is the modular synthesizer a musical instrument (like a guitar) or a piece of equipment (like studio gear)?

We believe that the difference lies in the intention of the user. Some users might approach the modular synth like a mastering compressor. This approach is more meticulous, thoughtful, almost "scientific" in its careful parameter editing, and thus calls for a verbal interface with labels, clean layouts, and maybe a “well-organized” topology in the Moog style.

While such textual interfaces have the advantage of being self-explanatory, they show both aspects of Saussure's definition. The word "gate" is a good example of arbitrariness, because it means two completely different things on Moog and Buchla synthesizers, and those who practiced only on one system might find themselves a bit disoriented the first time they work with the other. A good example of linearity is that you simply can't read two labels at the same time!

SF: Some other users, like us, may approach the synthesizer like a musical instrument, thus relying on a more physical interaction. For us, having to rely exclusively on text to tell the difference between two nearby jack sockets can be a waste of creative time. Instead, we found an interface design that rely on non-verbal elements, such as spatial distribution and colors, far more convenient. For example, once you know that a dashed line stands for semi-normalled connection, you can tell all the semi-normalled jack socket of a module at a glance. With this approach it is possible to play the modular synth like an instrument, relying almost exclusively on muscle memory.

Such a "nonverbal" approach, however, requires two elements: consistency and education. As for consistency, we try to keep our core elements the same across different modules. But the main thing is education, because road signs are easy to grasp only if you know what they mean. That’s why we’re investing so much in educational content like manuals, videos, and workshops.

PC: Your documentation, on the other hand, is deep. Something that is really interesting to us is that, unlike most modular synthesizer manufacturers, you don't have individual product manuals—you have a single, large, unified manual that describes all of your products. Moreover, it describes a lot of general synthesis concepts before relating them specifically to any of your products. How did the idea for this approach to documentation come about? What, to you, are the merits of approaching your product documentation in this way?

SF: I personally always loved vintage equipment manuals where the manufacturer didn’t assume that the user already had the theoretical background to operate the device. They always provided an introductory chapter on the fundamental concepts necessary to understand not only how the machine works, but why.

With the Manualone we wanted to replicate this attitude, thus providing introductory chapters explaining some core concepts of sound synthesis necessary to understand our modules. Of course, nowadays there are plenty of sources that explain the same exact things, and they are much easier to access compared to the 1970s. So, whenever we felt like an explanation would have been redundant, we just provided a bibliographic reference to a better source. A global “synth concepts” chapter in the beginning also helps us slimming down the individual modules’ chapters, since they can assume that the artist already digested the basics behind them.

Besides unifying the global concepts in a single document instead of repeating them for every module, a single manual helps us outline the similarities between modules and their interfaces through cross-references.

GG: A final, practical reason is that it’s much easier for us to keep the manual up to date if everything is in a single document, so that we can correct typos and update older sections as new modules come by. We are already at its tenth revision, and every time, I've had to fix a minor typo here and there. Our users are very collaborative in that regard, and they often send us tips on how to improve the document.

PC: The Frap Tools YouTube channel has also become a favorite resource and source of entertainment for a bunch of us at the shop. Obviously you make some straightforward product demos, but we love that you seem to put so much effort into documenting the non-standard uses for your equipment. We also love that you bring in concepts from the general world of music outside of modular synthesis and explain their potential implications for electronic musicians—I'm thinking of your videos about the harmonic series, about tuning systems, modal harmony, etc. How do you come up with ideas for YouTube videos? Do you have a specific motivation for going beyond basic product demos?

GG: The main motivation is what we said earlier about our instruments’ design: symbolic language has the advantage of immediacy and accessibility only if you know what the symbols mean. I think that we owe people good educational resources since we chose to go the cryptic way with design. We also want to push the education a bit further than “this does that”: you can’t learn a language if you only know what the words mean, you also need how to use them. So, besides telling you what the module does, we also like to add what you can do with the modules.

As for coming up with the ideas, I have two main approaches. First, I like to listen to people who are either beginners or completely uninterested in electronic music. When talking with them, for example at trade shows, or online, I always find that something that I was taking for granted is not obvious at all and can become the topic for a video.

The second approach is to draw comparisons between the world of electronic music and other instruments and traditions, especially the Western ones that I am more familiar with. An example is our series on modular expressiveness, which draws from the world of classical music.

PC: Your approach to the manual, and to your YouTube channel—it feels very community-centric. We also know that you host your own Discord server to connect to your users directly. How else do you think the connection to your customers affects the work that you do?

GG: It's fun because the very Discord server was an idea of some of our users, so I would say that our community has reached a point where it can modify itself—and this is just great to see. We are a relatively small company, and we have the huge privilege of connecting directly with our community. I don't know for how long we can keep up with it, but I hope it'll remain a vital part of our job because, besides being fun, it is also extremely useful.

From this direct contact we learn where our communication should improve, what aspects of our modules are clear and what deserve some extra documentation, and we also learn a few more ways of using them that we didn't think about.

PC: We've covered a lot—but we're curious, what's next for Frap Tools? Any special projects, or hints of what's to come?

GG: We have lots of project going on, most of which are still in the concept stage and we prefer not to disclose anything. However, we can say that the main focus for 2024 is the interaction between our system and the outside world.