The legend of BRENSO’s pulse-width modulation

video upload by Frap Tools

"PWM is a huge part of everyday electronics, but it is also a classic synth sound, to the point it reached a cult (if not meme) status.

A Eurorack oscillator like BRENSO wouldn't have been completed without a PWM section, and today we're exploring it in detail. It might not be the most obvious feature, since it is nestled into the timbre modulation section, but it is capable of wild timbers.

Check also this PWM patch: [video below]

Timbre and Amplitude modulation:
BRENSO Waveforms: [posted here]
Overtones: [video below]

00:00 Overview
02:36 What is a comparator and why it's important for pulse-width modulation?
03:36 The difference between BRENSO's square waves.
04:37 Modulating the comparator threshold to change the pulse width.
05:04 What are the harmonics of a pulse wave?
06:09 How to fake more oscillators through PWM.
07:15 Pulse wave symmetry and phase.
09:51 Feeding BRENSO's comparator with the triangle shaper

Pulse-Width Modulation and Sync with BRENSO | East Coast Sounds 1 | Frap Ideas

video upload by Frap Tools

"A recent article on @PerfectCircuit’s blog inspired this exploration beyond the label of "West Coast" synthesis. We thus focused on two techniques for the BRENSO oscillator that go beyond the classic complex oscillator's palette: PWM and sync."

Ryan Gaston’s articles:
Pt.1 https://www.perfectcircuit.com/signal...
Pt.2 https://www.perfectcircuit.com/signal...

00:00 Introduction: East Coast and West Coast?
02:20 Pulse-width modulation (PWM) on the BRENSO
13:29 The "AAAAAH" moment
14:05 Flip Sync


What are overtones and why they might be more important than you imagine

video upload by Frap Tools

"Today's topic ties together notes, harmony, tuning, timbre, and even more. It's the overtones, and this is our introduction!"

00:00 Introduction
00:22 What is a note?
02:11 What are overtones?
04:06 Harmonic and inharmonic overtones
06:24 Electronic waveforms and overtones: triangle, square, sawtooth
09:42 Isolate waveform partials through CUNSA bandpass filters
12:56 Create a complex wave through harmonics in analog
15:04 From the harmonic series to the dominant chord: closing remarks

Frap Tools: BRENSO | Full Demo and Review

video upload by Happy Mag

"The Frap Tools BRENSO is more than just a dual oscillator—it's a modern homage to the west coast synthesis tradition pioneered by Don Buchla in the 1970s. As a complex oscillator, BRENSO offers a dense web of internal modulation, wave shaping, and signal routing options that invite experimentation, creativity, and highly expressive sound design.

Let’s break down what makes BRENSO special—and why it’s a standout tool for modular synthesists and the perfect place to start Happy Mag's Synth Month 2025 journey!

🧠 What Is a Complex Oscillator?

In synthesis terms, “complex” usually refers to waveforms that go beyond simple shapes like sine, triangle, square, or sawtooth. These richer, more dynamic tones are achieved through audio-rate modulation—one oscillator affecting another at high speed to produce new, harmonically rich content.

To that end, BRENSO includes two triangle-core analog oscillators, each with four outputs. These oscillators are designed to interact, cross-modulate, and shape each other in ways that transform simple waveforms into entirely new sonic terrain.

🎨 We Love the Colour-Coded Interface!

One of BRENSO’s most elegant features is its colour-coded layout. This isn’t just for show—it reflects functional sections of the module, making navigation and patching intuitive:

🟢 Green Section – Frequency control for oscillator one
🟡 Yellow Section – Frequency control for oscillator two
⚪ White Section – Timbre shaping (via wavefolders and shapers)
🔴 Red Section – Amplitude control (via a four-quadrant multiplier for AM/RM)

These sections are organised spatially and visually, so once you understand the color scheme, you're halfway to mastering the module.

🔄 Modulation Without the Patch Cables

BRENSO encourages semi-normalled patching. Many modulation paths are internally routed by default using dashed lines on the panel. For example, the green sine wave is often pre-routed as a modulator for the yellow oscillator—no cable required.

This internal routing makes it easy to get rich interactions going quickly, but BRENSO never limits you: patching a cable into a jack overrides the normalization, giving you complete flexibility.

0:00 - Intro
0:04 - Review"

How does BRENSO generate its wave forms and how to win an extra analog sawtooth!

video upload by Frap Tools

"Today we'll explore BRENSO's core, its generation circuits, and by the end we'll add an extra waveform to the stock ones!

00:00 The 'canonic' analog waveforms: triangle, sawtooth, square, sine.
01:04 How does an oscillator generate a wave?
01:56 BRENSO's triangle and square waves
02:26 BRENSO's sine wave
03:27 BRENSO's sawtooth
04:47 How to create a second sawtooth with BRENSO, FALISTRI, and the 321
07:36 Double-sawtooth eas-coast fun and closing remarks"

NAMM 2020: Frap Tools Brenso Complex Oscillator Sounds & Interview

Published on Jan 18, 2020 Perfect Circuit

"Simone from Frap Tools gave us a walkthrough of the new Brenso complex oscillator—and entangled set of sound sources based on classic Buchla concepts.

Like many complex oscillators, Brenso is comprised of two oscillators with wave shaping and several options for internal modulation. Where Brenso differs is in its uncommon open-endedness: while most complex oscillators have relatively closed signal paths and surface only a few potential ways of interacting with each section, Brenso allows for lower-level, more entangled means of interacting with sound.

Frap Tools modules available here: https://www.perfectcircuit.com/frap-t..."

Frap Tools Brenso & 1010 BitBox Micro Eurorack Modular Synthesizer Jam

Perfect Circuit

"In this jam we used the new Brenso oscillator from Frap Tools as the main synth voice, the 1010 Music Bitbox Micro is providing the drum samples and the sequencing is provided by the Make Noise 0-CTRL and ALM Pam’s New Workout.

The Brenso is a dual oscillator capable of frequency and amplitude modulation as well as the ability to sync the oscillators to each other. There is also a built in wave shaper that allows you to dynamically control harmonics. The wave shaper section can also be used as a VCA, this allows you to just add an envelope generator and have a complete synth voice. In this video we used the Frap Tools Falistri to generate envelopes to modulate the amplitude and FM amount. One of the patches uses a little bit of filtering from the new version of the Mutable Instruments Ripples. Using a sequencer like the 0-CTRL for this type of synth voice works well since you can control the pitch as well as other parameters. We also added some modulation with the XAOC Batumi quad LFO.

The drum sounds are all samples from the new 1010 Music Bitbox Micro which is a smaller version of the original Bitbox, even though it is smaller it still has 8 channels and is a good option to add sampling to your eurorack modular. The drums are sequenced by the Pam’s New Workout used as a clock divider.

Brenso available here: https://www.perfectcircuit.com/frap-t...

Bitbox Micro available here: https://www.perfectcircuit.com/1010-m..."

NAMM 2020: Frap Tools Brenso and other modules

Published on Jan 17, 2020 CatSynth TV

"We speak with Giovanni Grandi of Frap Tools about the new Brenso module and get a demo of their full line of synthesizer modules. The video intersperses a description of the Brenso with a musical demo."

Wiggly LFOs on the BRENSO (credit: Make Noise)

video upload by Frap Tools

"When we saw this video on Make Noise's channel, we thought it was a great patch! [posted here]

So we wanted to recreate it on the BRENSO oscillator and use this technique in a different context. Basically, we're using an offset to throw the yellow oscillator at sub-audio rate and use the timbre modulation section to create some weird-shaped LFOs. We further expanded it through FUMANA, USTA, and FALISTRI.

Thanks again Walker and @MAKEN0ISEMUSIC for the inspiring patch!

00:00 Introduction
00:57 BRENSO yellow LFO
04:56 Adding a FUMANA Feedback
06:47 Clocking the USTA sequencer
10:00 Introducing a clock divider
12:20 Adding a second melody"

On Polyrhythms and Poymeters – live patching of Studio No.3 with Francesco Gennari

video upload by Frap Tools

"In today's episode, Francesco Gennari takes us on a true USTA masterclass, using it to weave a texture of four voices and a delay effect. Different pattern lengths and rhythmic structures create a complex and ever-changing harmonic and melodic landscape, but they also control the delay taps, pushing forward the limitations of sequencer-based compositions."

-Linktree: https://linktr.ee/francesco.gennari

Time stamps:
00:00 Introduction
00:18 Modular performance
02:53 Track Structure
03:21 Changing patterns live with Usta
04:01 First Voice: Brenso + Doepfer LPG
04:33 Bagai as a source of random modulation
05:07 Timbral shaping with Brenso
06:11 Second voice: Brenso + Doepfer SEM filter
06:45 Voice 3&4: Piston Honda MKIII + Optomix
08:29 Polyrhythmic interplay between voices
09:06 Ratcheting and randomness in Usta
09:44 Polymetric element in the ending section
10:35 Effects: Disting EX as a dual ping pong delay
11:22 Clocking Empress Zoia with Usta

Programming the bass sound of West End Girls on a Frap setup was a tough challenge (but we did it)

video upload by Frap Tools

"So we were asked to remake the bass sound of West End Girls by @officialpetshopboys with only Frap modules, and here's how we did it! It's not completely there but still seems like a fair approximation. Got other ideas? Let us know in the comments!

Interview with Stephen Hague:
http://www.muzines.co.uk/articles/tra...

Modules used (all of them...)
BRENSO: https://frap.tools/brenso/
CUNSA: https://frap.tools/cunsa/
USTA: https://frap.tools/usta/
FALISTRI: https://frap.tools/falistri/
CGM: https://frap.tools/cgm/
321: https://frap.tools/321/
333: https://frap.tools/333/

00:00 Introduction and original patch breakdown by Stephen Hague
01:21 The FM 'thump' on the BRENSO
03:31 The Jupiter 6 sound on the CUNSA
05:37 The Emulator II kick drum on the CUNSA
07:59 Adding variation through the Ping input and decluttering the patch
09:23 Changing the envelope fall through the USTA sequencer
10:34 Balancing the resonance with USTA's COMBO mode
11:06 Adding an extra sawtooth to the Jupiter 6 sound through FALISTRI
15:14 Final result and closing remarks"

On tape loops, clocks, and sequences | patching Studio No.4 with Francesco Gennari

video upload by Frap Tools

"In his fourth étude, ‪@francescogennarimusic‬ crafts a meditative track by integrating a tape multitracker and a modular synth. The key feature of this patch is the synchronization of the two machines, achieved by using a tape track as a clock for the Usta sequencer, which in turn clocks everything else, from Sapèl to the ‪@empresseffects‬ Zoia."

Time stamps:
00:00 Introduction
00:20 Modular Performance
04:13 4 Track Tape Loop Overview
05:08 How to sync a modular with a Tape Multitracker
05:48 Fostex Routing and Signal Flow
06:17 First voice: Brenso + Falistri + QSC
07:49 Second voice: Falistri + Doepfer SEM Filter
08:19 Third voice: Brenso + Doepfer LPG
08:33 Gate randomness with Usta Variation
09:25 Writing melodies on Usta with external keyboard
10:09 Clocking Sapèl
10:30 Processing the tape with the Random Source Wave Multiplier
11:41 Empress Zoia - Dual independent Effect Chains

More glass sound with BRENSO

video upload by Frap Tools

"The bright TZFM of our BRENSO allows us to get these bright and cheerful glass sounds! We patched an envelope to control the FM deviation, then a slow LFO to control SAPÈLs main clock. The sequence is random, of course, thanks to USTA’s variation capabilities!"

BRENSO and beyond (with some FUMANA feedback)

video upload by Frap Tools

"Animating BRENSO's final output through FUMANA's bands and some feedback!"

On counterpoint, cross-FM, and analog+digital timbres | Studio no. 5 performance & patch breakdown

video upload by Frap Tools

Today Francesco explores one of the harshest timbres ever created by mankind: the cross-FM. And if that wasn't enough, he will use both digital AND analog FM at the same time, blending Brenso and Hertz Donut mk. 1. How can we tame such wild beasts? Through a careful composition in the spirit of the great counterpoint masters.

Original track 'Studio No.5' composed by ‪@francescogennarimusic‬"

Time stamps:
00:00 Introduction
00:22 Modular performance
03:14 On counterpoint
03:55 Track structure overview
04:24 First voice: Brenso + Doepfer LPG + QSC
05:39 Layering the first voice
07:16 Second voice: Hertz Donut MKI + Optomix + QSC
09:33 Third voice: Falistri + SEM VCF + QSC
10:24 Usta clocking Sapel, Bagai, and Empress Zoia Delay
10:52 Disting EX: Ping Pong Delay and Reverb
11:33 Desmodus Versio: Final Reverb
11:51 Mute Hack with Usta and 411 VCA

On cross-FM and fake polyphony | Performance breakdown with Francesco Gennari

video upload by Frap Tools

"In today's video, ‪@francescogennarimusic‬ walks us through the creative process behind his first study for modular synthesizer. It explores three main concepts:

1) Cross-FM with the Brenso oscillator: https://frap.tools/brenso
2) Fake polyphonic strings with the Verbos Multi Delay Processor
3) Creative uses of the mute function through the QSC Quad Stereo Channel and the Usta Sequencer. https://frap.tools/usta https://frap.tools/qsc"

‘Glass sounds‘ analog through-zero FM patch breakdown with Brenso and Cunsa!

video upload by Frap Tools

"As per request, here's a patch breakdown of this short video: [posted here]

It's a super crystalline sound thanks to Brenso's through-zero FM, and we took it a bit further by adding the Cunsa filter, which we didn't have back when the short clip was filmed."

BRENSO EXPLORATIONS: Drone #01

Trübüla

"A little Drone based on Brenso + some Falistri processed by Fumana."

Frap Tools Magnolia, 8-voice analog thru-zero FM polyphonic synthesizer | Project update

video upload by Frap Tools

Click CC at the bottom of the player for subtitles.

"Magnolia will be an 8-voice analog through-zero FM synthesizer, which we built to create sounds from the modular world through a classic keyboard interface.

Waveshapers, wavefolders, and, most importantly, analog linear through-zero FM unlock every sound associated with the 'West Coast' synthesis world. But that's not all! Fat resonant filters and powerful analog oscillators allow more traditional subtractive synthesis sounds as well.

A vast and flexible modulation section encourages complex patches with the twist of a knob, but it is always easy to keep track of what's going on thanks to LEDs on every source and destination. An arpeggiator and a sequencer complement the machine.

We are announcing and showcasing two pre-production units. We aim to release the final version at the end of summer, and it will show some differences. It may have a more refined interface, it will feature digital effects, and some of the features currently under evaluation may disappear.

We've been working on it for the last year, and we're eager to show it to the world!"

Follow-up to this post where you'll find additonal pics.

Update: press release follows:

Frap Tools to take on high-end keyboard synthesizer market with ‘West Coast’ MAGNOLIA making its public debut at SUPERBOOTH25

MEDOLLA, ITALY: Frap Tools, hitherto known as a manufacturer of Eurorack modules and accessories alongside professional audio compressors in the 500-Series format, is proud to venture into the world of high-end keyboard synthesizers with its introduction of MAGNOLIA — announced as an 8-VOICE ANALOG THRU-ZERO FM SYNTHESIZER built to unlock every sound associated with ‘West Coast’ modular synthesis through a classic keyboard interface — anchored around showcasing two pre-production units at SUPERBOOTH25, May 8-10, FEZ-Berlin, Germany…

As an 8-VOICE ANALOG THRU-ZERO FM SYNTHESIZER, MAGNOLIA unlocks every sound associated with the so-called ‘West Coast’ modular synthesis world with waveshapers, wavefolders, and, most importantly, analog linear TZFM (Through-Zero Frequency Modulation) Indeed, its intentions are made clear from the outset by the on point wording worked tastefully into its (initial) top panel design. No need to necessarily remain there, though, for fat resonant filters and powerful analogue oscillators also allow for more traditional subtractive synthesis sounds. And although a deep and flexible modulation section encourages complex patches with the push of a button and twist of a knob, switching modulations on and off with the TOGGLE function, it is always easy to keep track of what is going on thanks to the inclusion of LEDs (Light-Emitting Diodes) on every source and destination.

Digging deeper, MAGNOLIA features eight analogue voices with two oscillators — carrier and modulator — and 24 dB/oct resonant HIGH-PASS and LOW-PASS filters; the carrier oscillator has a through-zero core for precise, sideband-rich analogue FM (Frequency Modulation) sounds, so crystal-like pads to growling basses are available to all with the greatest of ease, while FM can be applied to the filters. Furthermore, sculpting sounds that have not been heard before on analogue polysynths are now perfectly possible, thanks to MAGNOLIA’s unique signal flow — think continuously variable waveform shapes and a wavefolder circuit per voice!

Those two oscillators are derived from Frap Tools’ BRENSO (https://frap.tools/products/brenso/), a Euroack module readily representing its creator’s primary analogue source of articulated waveforms whose degree of entanglement can be precisely set by the musician. MAGNOLIA’s Oscillator 1 is the ‘West Coast’ one with TZFM, wavefolder, and FLIP SYNC, while Oscillator 2 is the ‘East Coast’ one, with PWM (Pulse Width Modulation) and fine-tune. Whether wanting experimental FM sounds or punchy synth brass, they are always at anyone’s service. Speaking of Frap Tools’ unique modular soul, MAGNOLIA’s filter section is derived from CUNSA (https://frap.tools/products/cunsa/) — itself a quadruple analogue ping-able multimode resonant filter, saturator, mixer, and oscillator, no less!

Musically, MAGNOLIA sports a keyboard from fellow Italians FATAR, with polyphonic aftertouch capabilities for enhanced expressiveness, while a per-part ARPEGGIATOR and per-part 16-step SEQ (sequencer) serve to creatively complement the synthesizer still further. Features briefly worth drawing attention to here by way of ending on some more high notes include MAGNOLIA’s bi-timbral programs (with SINGLE, MORPH, DUAL, and SPLIT MODES); all-analogue signal path; three loop-able DAHDSR (DELAY, ATTACK, HOLD, DECAY, SUSTAIN, and RELEASE) envelopes; three digital LFOs (Low Frequency Oscillators); and 512 preset memory slots.

Anyone attending SUPERBOOTH25, May 8-10, FEZ-Berlin, Germany can get up close and personal with two MAGNOLIA pre-production units by swinging by Booth B049 there. Their creators will be showcasing them personally, eager to show the results of their hard work, while providing a passionate warm welcome. Frap Tools aim to release MAGNOLIA as a production product by the end of summer, albeit with some differences evident by then. The interface will likely be more refined, featuring digital effects, while some features currently under evaluation could conceivably be removed."

What is filter pinging (and filter ringing)? A demo with BRENSO and CUNSA

video upload by Frap Tools

"Today we'll see what's filter pinging, how to ping a filter, and why it can mean more things."

00:00 Introduction
00:13 Chris Meyer's definition of "pingable"
02:08 Pinging BRENSO and CUNSA
06:20 CUNSA's Combo Mode
08:06 Pinging a resonant filter: analog drums
09:26 Allen Strange's definition of "Ringing"
10:32 Ringing CUNSA
12:25 Adding V/oct and ringing more filters at once
14:19 Closing remark: filter pinging and filter ringing

New Magnolia Keyboard Synth by Frap Tools Coming to SUPERBOOTH

via Frap Tools

Update: video here

"And here's what we'll bring to Superbooth: Magnolia is the prototype that kept us busy over the last year. It's gonna be an 8-voice analog throuhg-zero FM polyphonic synthesizer. At its heart, all the sounds you've met in our modules: Brenso, Cunsa, and so on. We could say a 'west coast polysynth', but it's capable of analog subtractive synthesis as well. We'll bring two pre-production units at @superbooth_berlin , so come check them out and stay in touch for some video and audio stuff!"

CLICK FOR MORE »

Frap Tools CUNSA in-depth tutorial | Eurorack quadruple multimode analog filter module

video upload by Frap Tools

"Time to dive deep into Cunsa's main features! In this first tutorial, we will explore how a single filter works and how to combine them together to get the signature "Cunsa sound." This should get you started with CUNSA and let you understand its basic functioning. In the next episodes, we will see more specific applications!

00:00 Intro & Cunsa overview
02:21 The 12 dB/oct lowpass filter
02:41 The Q parameter (resonance, emphasis)
03:42 How the Q affects the LPF cutoff point at 12 dB/oct
04:15 The Character parameter
05:15 Combining Q and Character
05:55 The 24 dB/oct lowpass filter
06:10 The Character behavior on the oscilloscope (12/24 dB/oct LPF)
08:00 How the Q affects the LPF cutoff point at 24 dB/oct
08:15 A comparison of the 12 and 24 lowpass curves with different Q settings
08:52 The 12 dB/oct bandpass and highpass filters
10:09 How Q and Character affect the bandpass and highpass curves
10:23 The Behavior switch (filter and combo mode)
11:50 CV inputs for cutoff, Q, and Character
12:31 Using CUNSA as an oscillator (self-resonating filters)
13:13 Oscilloscope views of the self-oscillating filters
13:37 Fine-tune cutoff frequency knob
13:46 BONUS TIP: double TZFM oscillator with Cunsa and Brenso
14:12 The Ping circuit: nonlinear integration
15:40 Ping circuit and combo mode
16:10 Ping v/s ring, a brief recap
17:03 Semi-normalled connections
17:19 The mixed outputs
18:19 The routing switches: complex filtering with four filters in parallel
19:45 Some examples of semi-normalled patching techniques
22:13 The Dry output and other complex patching examples
25:50 Outro"