My hybrid Synthesizer

Analog Modules and CV / DSP via Computer (Max/MSP)

I enjoy the possibilities that digital music electronics offers. Max and M.A.R.S. have already completely eliminated any escapements. In the digital world, however, I lacked a kind of sensory factor. Quite different, whether I use a digital or analog filter. The analog filter always shows an individual characteristic.

With the appearance of the Expert Sleepers modules (Audio-to-CV and CV-to-Audio), it was clear to me to start an experiment and connect Max/MSP and the Synthesizer.

Since the chosen modular synthesizer format (e.g. Eurorack, MOTM, MU or Buchla) is irrelevant and rather a question of the personal taste, I write mainly about the aspects in Max/MSP. The Expert Sleepers modules are only available in Eurorack format - but this is also irrelevant, because (almost) all formats have 10Vpp CV. An audio interface is required for the connection between Synth and Computer. Here is an overview of my instrument.

The instrument is designed for 4 channels to work with an audio interface. The 8 analog inputs are for 4-6 channels from Buchla and 2-4 microphones. 4 outputs are available for the speakers - the remaining 4 outs may run e.g. into the Buchla, which itself also has a microphone input. The CVs are transmitted digitally (SPDIF).

Although the computer is "active" (software), however, I do not want to "serve" (operate) it and it should rather be on the side. For Control I use iPads and a Seaboard RISE.

    Big Upgrade Summer 2018

    Both Apple and Metric Halo have finally come up with the big changes that have been expected for years! At Apple, this is the cutover to Thunderbolt3 (with USB-c connectors), strong 6 core processors and faster DDR4 Ram. Since this also involves a change in the periphery, I wrote something in more detail about it: Macs 2018.

    At Metric Halo, the much-anticipated 3d upgrade is now available. Conspicuous are the cutover to "Audio over Ethernet" (instead of Firewire) and the introduction of the "Edge Cards". They offer the possibility of variable interface personalization. Edge cards are available with MADI (Copper or Optical), AES, ADAT, SPDIF and MIDI - also for later retrofitting.

    The best is the MH-Link! Especially in the realization of a hybrid instrument, the doors are now wide open! Often I ran out of channels because 8 analog I/O's are just not enough, especially if there are microphones in addition to the synth. The MH-Link can now connect up to 8 audio interfaces via Ethernet and they are recognized by the computer as one logical audio interface. Thus, several interfaces form a modular interface in the desired size! If I understand correctly, 0.02ms latency per interface is added (with 8 linked interfaces 0.16 ms). That's as good as nothing!

    The picture shows my "small" setup (in front and back view). The blue device is a room simulator (Quantec Yardstick) and the red device is an 8ch unbalanced / balanced converter that converts the synth signals better than a DI box. The setup has become simpler and much more powerful.

    What should be analog and what digital

    First of all, I had chosen the function modules for the digitization, since they have a smaller proportion on the sound, but rather "organize" it. Gates, Triggers, Envelopes and LFOs seemed to me indistinguishable, and when, on the contrary: control voltages are produced by the computer with much higher precision! Due to the size and the prices, the Sequencer modules also came first. They often require expander modules for modulation or control - it is probably the (spatially) largest and also one of the most expensive areas of the Modular Synth.

    The most important modulators might be LFOs - also here I do not believe, to be able to hear a difference between digital and analog - in the case in which the LFO frequency goes to the Audio range and I should be dissatisfied, I still have analog Oscillators. Many modules offer a switch from Oscillator to LFO.

    The third large area for digitization is the area of Random Generators. Most Random Generator modules work digitally anyway. Here, the computer offers endless approaches. First I was interested in the Shift-Register and Noise based ways to Random, as in the Wiard Noise Ring.


    The approach is, of course, to emulate existing modules as much as possible one to one. Interesting and instructive were experiments with my Shift-Register-Randomizer Max-Patch, based on the Wiard Noisering module. Random is, in my opinion, far more multifaceted when done by the computer. The hardware modules operate usually at a built in 8-bit width, i.e., they only have 256 steps. For Max programmers, this might be rather unsatisfactory. More about the implementation in Max can be seen on the right side.

    This is a Low-Frequency Trapezoid Generator - unmodulated in the left window, ring-modulated in the middle window and with the same sine added from the LFO in the right window.

    In some cases, e.g. the staircase generation by means of S/H it is possible to produce melodic/harmonic intervals in precise Hz data for the pitches. This is not possible with analog S/H modules.

    Two (software) sawtooth waves (SAW), e.g. 10.07 Hz and 8.52 Hz run into an S/H object and result in a certain stair pattern, which is sent as a CV control signal to the analog Oscillator. A predetermined intervallic structure can thus be retrieved.

    The Sequencer

    functionally largely corresponds to its analog relatives. Max for Live provides a very good GUI object for this application. Because of the possible availability of several software sequencers, I have so far dispensed with various gate buses, as they are common with analog machines.

    A typical Rock/Pop sequencer example.

    By incorporating the tempo as a variable, much more abstract sequences can be generated.

    There are pitch, velocity, duration, cut-off and panorama controls and two additional placeholders. The duration value refers to Legato/Staccato style and would be analogous to Pulsewith. Up to 64 steps can be played forwards, backwards, back and forth, rotating or randomly. Instead of the jump switches on analogue sequencers, the beginning and end of the steps to be played can be defined/varied by a bracket or numbers for the beginning and the end (in the picture it is from 3 to 13).

    More "Modules"

    Some things should be in virtualized form. These are Envelope Follower, Digital Shifter, Ring Modulation, Comb and Formant Filters, Bit Reduction and more. Of course, it is also obvious to use VST plug-ins e.g. Reverbs. All this can look like this:

    The visualization of the LFOs and the possibility of Presets are welcome side effects!

    More Complex Filters

    At the beginning still following the example of my EMS Filterbank, I had programmed a fixed Filterbank with extreme slopes. On the picture's top is the part that is cut out at the bottom.

    By using a compressor, the selected bands can be given an increased presence - thus creating interesting sound surfaces/discs, which alone can also be fine. The Filters are made with the Max-objects [cascade] and [filterdesign].

    In the picture on the right, the selected original band is shown at the top and the same sound after the Compressor makeup at the bottom.

    For a friend I ported the Filterbank to Ableton as a Live PlugIn - with some extras.


    A big project for the hybrid Modular Synth! Here is my resynthesized voice. There is no voice recording - even at the beginning! What is to be heard are 16 sine waves resynthesizing what I'm talking into the microphone. Amazing how good my voice is recognizable! By reducing the number of sine waves, the chirp-like sounds are produced.

    This is possible through Miller Puckette's Max-Object with the most versatile name: [sigmund~].


    - is the key to the playability of the hybrid modular synth. For myself, I have developed a kind of browser (computer), in which all areas, separated from each other, are set. I play through my interfaces, one or two iPads and a Roli Seaboard Rise, and the computer does not have to be in the field of view. The screenshot shows at the top (gray) the "tabs", by which a very pleasant order is created and each area can be adapted to its function. The whole thing is similar to the "Preferences" in a software. Seen are the settings for the RISE:

      More about the Seaboard RISE here

    Why so little MIDI??

    MIDI (7 bits) has too few gradations with 128 steps and is also rather too slow (ms). 48 kHz, sample accurate in 16 bits (Expert Sleepers' Audio to CV) are simply another league. Nevertheless, MIDI still has its place (for example, Roli Rise). For sliders and pots, I now prefer my iPads, picosecond-fast and 14-bit wide.

Expert Sleepers ESX 8GT

Using Gates individually
  • Since I'm pretty sure that the triggering of the desired gates of the ESX 8GT, from Max, is a problem for some people, here is a converter patch (binary to decimal). Each combination of On/Offs on an 8-Gate provides 256 possible positions (8 bits = 0 to 255). This value is then routed to the input of the [es4encoder ~] Max object. Bingo.

    The Max-objects for Expert Sleepers Modules are here.

Download patcher


flash the FSM easier
  • The MIDITEMP FSM (Footswitch to MIDI) is for the connection of 2 pedals and 2 switches. The configuration is transferred with SysEx data into the device and is complicated for the "normal" user and unusual. To create simple changes or "setups", I programmed this little software.

Download Flasher