In this post I continue selecting the DIY modules for my custom modular synthesizer build by selecting the sequencers. Due to the length of this post, I won’t select any MIDI / computer interface or quantiser. In the case a product has one in-built, like the Mutable Instruments Yarns, I may end up choosing one.

The current selection for my DIY modular synth is as follows (show with native faceplates):

You may notice that I’ve added a couple of Pure VCAs since my VCA post to boost up the numbers to four. Apart from that I’m still a couple envelope generators and an LFO or two short.

You’ll notice I say sequencers, as in plural. The concept is that I have a sequencer or arpeggiator to drive a bass-line, and a multi-channel synthesizer to drive melody and chords. So theoretically I can use the Orgone Accumulator for bass, and the Living VCOs for chords, or lose one oscillator from the chords and add it to the bass. This is a musical approach which is one of my targets, rather than just experimentation, although that will also occur when I select all the “utility” modules such as dividers, multipliers, buffers etc. Hence, I’m building a pretty standard synthesizer architecture (albeit fully modular), and will build flexibility for experimentation around that.

Note that I won’t end up with true polyphonic architecture, where each voice is a full synth voice, and each note pressed re-triggers your envelopes for filter and amp. Instead, I’ll get one shot duo/tri-phonic arrangement where all the oscillators are mixed and share a filter etc.

In terms of sequencer requirements, I’m fairly flexible. I haven’t owned a stand-alone sequencer before, but apart from a few drum modules my Korg MS2000R has what I’d call a standard sequencer. It has 3 channels you can route to different parameters in the synth such as pitch, pan, and even waveform selection. So, the more channels of sequencing the better, but one last point… The sequencing must be simple to program, and if possible, not overly simple. This may be a contradiction, but I don’t want to spend my time menu diving or referring to reference guides every time I want to make a tune, yet it should have some nice simple features to mix things up (like reverse or looping certain steps). The best comparison I’ve discovered would be an Oberheim Two-Voice Pro, which allows you to sequence the two voices separately.

Requirements:

• Sequencer or arpeggiator to drive bass-lines
• Chord sequencer
• Sync between the two sequencers
• 16 steps or greater preferred but 8 considered (any less won’t be considered for selection)
• Preferably extra channels of sequencing of non-pitch parameters (worst case I can take the CV out and mangle it through other modules via a buffered multi)
• Some ability to modify more than pitch on the fly, such as reverse, freeze, looping, transpose, slew etc
• Quantisation is required (separate modules may be required)
• Gates out of each step is an added bonus
• Skiff friendly

If I cannot achieve these requirements, either due to lack of DIY modules with those features or cost, I may choose to omit some or all of the sequencing and do it externally or via MIDI.

That’s enough rambling, here’s the initial selection process of all modules.

GMSN! Pure Sequencer & Quantiser

Since GMSN! came back online and have gone open source, I’ve been a fan of their modules as they prove a great base set of modules which can be built or customised as desired. The Pure Sequencer is an 8-step sequencer with direction, range, clock in/out, pause, reset, slew and has gate outputs per step. They also make a quantiser which can tune all those odd voltages to notes.

Overall it’s a pretty simple yet effective combo, and will be considered for the bass. The spacious design and slider controls should be noted here with merit.

Manufacturer’s link: https://gmsn.co.uk/products/gmsn-pure-sequencer, https://gmsn.co.uk/products/gmsn-pure-quantiser

RYO VC Sequencer

Like GMSN!, I’ve already selected a RYO module for my project, the Optodist. The next similarity is their VC Sequencer, an 8-step sequencer akin to the Pure Sequencer but with positive and negative voltages per step. With the gate expander you also get the gate outputs per step, and you can run use units to give you 16-steps, however 16-steps of knob twiddling in four vertical rows is ideal. Also featured is a reset and forward / reverse modes, and clock in/out. With the VC you can use voltage to control the step direction (e.g. triangle provides a pendulum sequence, saw wave is back, and anything in between these and other waves) which is a great feature. You can also run it at audio rates to generate a waveform, and the knobs effectively shape that waveform. Again like the Pure Sequencer the VC would need a quantiser.

Due to the similarity of Pure Sequencer that’s the target to beat. Unlike most Eurorack systems I’m not looking for space reduction, so the compact advantage of the VC doesn’t apply. Given the added feature of voltage control for step direction this makes it through to the final round for the bass.

Razmasynth VIII

The Razmasynth is an interesting looking module. At its heart it’s another 8-step sequencer, although it’s main feature is its 8 playing modes (Forward, Backward, Forward/Backward, Pendulum, Crab, Crawl, Random, Brownian). It also has trigger mute buttons per step, and reset. It doesn’t have slew or individual gate outputs per step.

At first I was put off by the type of potentiometers used, but a quick look at the build guide indicates I could use the same 9mm Alpha pots I’m using on most of my equipment. At 50 euros for the kit and AU$40 for the common parts, it comes in at a reasonable price. This comes close into consideration for bass, but given the RYO VC also has adjustable modes (via voltage control) and offers gate outs the VIII just falls short.

Manufacturer’s link: http://www.razmasynth.com/io/VIII.html

Synthrotek Sequence 8

There’s yet another 8-step DIY sequencer on the market, the Sequence 8 from Sythrotek. At first glance it’s similar to the RYO, but for a slightly more expensive price it offers some additional features. Firstly, it has 3 CV outputs with voltage limit controls, which could be used to drive three oscillators or sent to a filter etc. It also has clock in/out with coarse and fine control over the internal clock, and gate outputs per step, and a hold/freeze feature using either manual pushbutton or the current step. Then, it has a controllable random feature which introduces random stepping/stutter in the sequence, and the ability to manual step through each step with a pushbutton.

Like the Pure and VC sequencers above, a quantiser would be preferable (to avoid a lot of manual tuning), however the advantage of the Sequence 8 is the multiple CV outputs without the need for a buffered multiple and attenuator, so for a bass you quickly change more than just the pitch. For this and the other extra features, it makes it through to final selection.

Manufacturer’s link: http://www.synthrotek.com/products/modular-circuits/sequence-8/

Division 6 Dual Mini Sequencer

I thought I’d include a picture here to do this tiny thing justice (and because there’s no video showing the dual version). Division 6 have managed to cram a lot into a tiny package. It has 2 x 16 step sequencers which can be daisy-chained to make a 32 step, or the second sequencer can be used to transpose steps on the other. It’s limited to 5 octaves, however the little keyboard can be used to play notes when not sequencing which is useful. In addition to the gate out, it has an accent out which can be programmed per step to trigger something. This too makes my shortlist for the bass sequencer. Despite not seeming to have reversal and other similar options, the two sequencers means you could use one for bass pitch and another for something like filter cutoff. It also has more steps that the options so far and comes in at only 90 euros for the kit.

Manufacturer’s link: http://division-6.com/products/dual-mini-sequencer.php

Din Sync ModSeq

The ModSeq is a an 8-step sequencer from Din Sync who make the quite awesome TB-303 cloning modules. This product is a quite different to a TB-303 sequencer or anything above, in that it uses four controls to set pitch for the 8-steps. So pitch setting 1 gives you the first step’s CV, and the opposite in the CV range is set for step five. Then knob 2 gives you two and six etc. Using their analogy it’s like a sample and hold. It also has a reset so you can make it a basic 4-step sequencer.

The ModSeq comes it at around half the price of the RYO or Synthrotek, but doesn’t seem to be available any more in kit form. Otherwise I would consider it as a option based on price alone.

Manufacturer’s link: http://www.dinsync.info/2013/01/introducing-modseq.html

Cavisynth SEQ-UFD

The great thing about Eurorack is you’re always discovering new manufacturers. Cavisynth of Switzerland is one such manufacturer I found from Googling around (and sorting through Modular Grid is another).

Basics first, it’s an 8-step sequencer with gate out per step, internal/external clock and reset. It also has seven play modes, including forward / back / crab and random.

There’s also a knob to manually control the step you’re on, which is nice as it allows you to quickly skip back and forth to compare pitch with the previous step. But this is only in SS mode. When you change to the forward mode, that knob limits the steps in the sequence from 1-8; brilliant! There’s also a range limiting knob to similar to the outputs on the Synthrotek, and a mode which seems to jump steps based on the control voltage coming in.

Some modules seem to resonate with me, and this is one of them. It has a great set of features and is Arduino based and open source. It’s only EU22 for the PCBs, and judging from the parts list looks around half the cost of the Synthrotek or RYO. Could be a winner for the bass sequencer. Only one concern is the depth, as one PCB is parallel and the others are perpendicular, however they aren’t that deep. As I plan to put the sequencers at the bottom of my synth (either on a bottom “row” or where a keyboard would typically be), I could make that section deeper as I need a spot for the power supply anyway, so I may be able to work around this.

Manufacturer’s link: http://cavisynth.com/product/seq-ufd/

Shakmat Modular Bishop’s Miscellany

If the Cavisynth SEQ-UFD resonated with me the most thus far, then the Bishop’s Miscellany has that resonance going into self-oscillation! But how to describe it?

It has two channels, each being able to record up to 32 steps, so you need a pitch CV input from a keyboard, other sequencer, arpeggiator etc. Once recorded you can limit the steps, change the part of the sequence you’re playing using the shift control, and switch between sequences. All these parameters can be CV controlled. You can also do basic chords (refer to the second video below) which could be an option. You also get a couple gate outs and random voltage generator (which can be use to drive its pitch). The price is EU160 + shipping, so not cheap but in line with other offerings. This makes it through to the final round for both bass and chords, and due to being only of the most fun and musical options here. I suggest you check out these quick videos to understand the unique workflow on offer.

Manufacturer’s link: http://www.shakmatmodular.com/products/bm.html

Klee

The Klee is a beast of a sequencer, which looks more like a traditional sequencer akin to a Doepfer Dark Time. It can run as a typical 16-step or 2×8-step sequencer, however, it’s more than that. It’s also a bit-step sequencer, which means that as you activate each bit, the values are summed together to get a different sequence. For example, if you use two bits and set the variable range to 1-octave, the first bit gives you one octave, and the second extends this to a second.

Running through some other features you can adjust those intervals on the fly with the big knob in the middle, change the range or add randomness, glide for parts A and B (each of the 8-step parts) and much more. It’s also one of the best looking sequencers out there, and definitely invokes some gear lust.

The Klee is something that looks simple enough to use at first, but has a lot of depth to it. My main issue is whether it’s overkill for what I need it for. To get the kit with the daughterboard is US$365, then the parts etc, I could imagine spending over US$500 on this (in fact the full kit is US$515), which is well beyond my budget and for this reason I’ll pass. But for those wanting a large hands-on sequencer, an alternative to a Dark Time or a Korg SQ-1, and don’t mind laying out the dollars, the Klee a great option to look at.

Manufacturer’s link: http://www.birthofasynth.com/Scott_Stites/Pages/Klee_Birth.html

Mutated Yarns

Yarns is the first sequencer here that includes a MIDI interface, and provides a lot of flexibility. It has 4 channels of CV and gate, an arp, euclidean sequencer, and a Roland SH-101 style step sequencer. It also has a built-in digital oscillator with 5 waveforms plus noise, and can do legato (tying notes together) and portamento (glide) . A great feature set, but is it easy to use?

You can input notes on the step sequencer via a MIDI keyboard, or via the click wheel control plus buttons for ties and rests. The note value is displayed on the screen, and you can save 8 sequences. Choosing modes is done by putting the unit into a particular state, then pressing the number of keys on the MIDI channels you desire to set it up. So 1 note gets you into monophonic mode, 4 notes quadrophonic, or 2 notes on different MIDI channels provides you with 2 part multi-timbral. Trigger mode is done by sending notes on MIDI channel 10.

MIDI is via your standard DIN connector, not USB. I generally prefer USB as I run all my MIDI via USB hubs, although I do have MIDI/USB interfaces for older gear like my Korg MS2000R and my Oberheim/Viscount OB12.

What’s apparent from the video below is that every function in itself is relatively simple. However, every extra step, such as adding portamento or changing the part your editing requires more digging, and that’s when it becomes more of a technical task than a creative one. As far as functionality goes and bang for buck, not much comes close to the Yarns. It’s only US$7 for the PCB, and under US$100 for all the parts. For this reason I’ll consider the Yarns in my final selection. When it comes to fun factor though, other modules, especially something like the Bishop’s Miscellany top the Yarns.

Manufacturer’s link: http://mutable-instruments.net/modules/yarns

Ornament & Crime

Ornament & Crime is digital multi-function modules (running of a Teensy like the Orgone Accumulator), called a polymorphic CV generator. I’m not sure what that means but I’ll try to explain what it does! There’s:

• A quantising analogue shift register which is like a sample and hold
• A triad chord generator (could be perfect for the Living VCOs), with different ways of generation (via different apps)
• A pitch quantiser in two versions
• A wavetable quadrature LFO (effectively 4 sine waves running at different phases)
• A modulation generator based on some mathematical systems
• A quad voltage-controlled envelope generator
• A dual-channel step sequencer with 4 x 16 step sequences
• A ping pong envelope generator
• A quad “byte beat” equation generator for 8-bit sounds
• A reference app which spits out voltages for reference and tuning

That’s an extremely simplified account of what it does! It’s prudent to mention that some of the apps are based on open source Mutable Instruments code. Of course you can edit or add your own apps, which isn’t my intention for this project but something for the future.

I’ll focus on the sequencing here, the chord generator and the step sequencer, called Harrington 1200 and Sequins respectively.

The Harrington 1200 mode takes a CV in and quantises it to the root note of a triad (i.e. the lowest note of a three note chord). It then generates the rest of the chords at the CV outputs, using neo-Riemannian music theory (watch the video below for a quick explanation). You can use the triggers to change the intervals of the chords (e.g. between major and minor), transpose the root note, or perform inversion (e.g. taking the highest pitch note and throwing it down to the bottom under the root note). A consideration of this mode is that you still need a sequencer. In my application the bass sequencer could provide the root not while this generates chords. Or, I could throw any quantised voltage in an add chords to that. It may not be the most standard musical approach to chords, but could provide some interesting results.

The Sequins is the step sequencers that requires an external clock and provides sequencing up to 16 steps. The programming involves numbers rather than notes which isn’t ideal, although this could be hacked. You can loop through multiple sequences; 4 x 8 step sequences on a single CV output for example. One advantage of the O&C is the OLED display, which I’ve seen in action. It provides the ability for multiple lines of text, and a far greater advantage in terms of usability than the Yarns or other Eurorack modules like a Disting MK3. However the step sequencing isn’t as immediate as using knob or slider controls.

You can purchase a PCB with pre-soldered SMD components for US$140, or the PCB for just US$10. Apart from the OLED and Teensy, the rest of the parts don’t seem too expensive. I’m guessing if you did the SMD yourself the whole thing would cost under US$100, which is quite amazing for what it does. The question for this module for this project is whether it’s going fit. For my normal Eurorack, I’d like to get one at some stage. Despite the step-sequencing seeming a little tedious, the chord generation is experimental but quite enticing as you begin to think about how you could control them. This makes it through to the final round. It also covers off a lot of other functions.

If you want more videos, VCL has a series on the Ornament & Crime, just follow the playlist.

Manufacturer’s link: http://ornament-and-cri.me/

Music Thing Modular Turing Machine

The Turing Machine is an interesting modules which can be expanded for more functionality. At its heart it is a 2-32 step sequencer, which can generate a random voltage, which in turn can be captured to repeat a section, “lock the loop”.  A scale knob can limit the range of the pitch generated. A quantiser is needed to set the random voltages to notes.

The Volts Expanders can be added to generate an additional CV output from the 5 knobs, to be sent to parameters such as filter cutoff or anything else your heart desires. The video demo shows that if you quantise the Expander’s output, you can start getting duophonic sounds, and you can add more VoltsExpanders for chords, and it does sound quite musical but requires multiple quantisers or manual tuning.

Another cool yet non-sequencer type function is that you can send in an audio rate clock (e.g. square wave from an oscillator), semi-lock the randomness, and generate a chip-tune type oscillator sound. This can also be achieved via the Expander, and using the knobs you can shape the waveform… nice! Mix the expander and the main module and things get even more interesting.

Other expander modules include the Pulses clock divider, and Voltages which provides an eight step random looper with illuminated sliders, providing even more control and options, and a vactrol mixer modules. Other people also provide expanders like the Bytes for more complex time signatures.

So it appears like once you enter the Turing world, you expand its capacity and open up so many options. For bass its nice and flexible; for chords it’s possible but trickier. It’s 15 GPB for the panel/PCB set, and there’s nothing particularly fancy about the ICs. It has no Teensy or Arduino in the background, and seems like a cheap option. I’ll consider this in my final selection.

Manufacturer’s link: http://musicthing.co.uk/modular/?p=1391

Hexinverter Orbitals

A quick mention here of the Orbitals module which is discontinued. Hexinverter have also stopped making new DIY modules. It what I’d call a more traditional step sequencer and would’ve been a great option.

http://synthcube.com/cart/hexinverter-orbitals-panel-pcb

Doboz Prizma

Whilst looking for a quantiser, I stumbled across another sequencer on Modular Addict. Like the Cavisynth I was excited to see a new company, especially one that makes a nice and colourful module.

The Prizma is a dual 16-step sequencer. With the 16 LEDs down the side you get visual representation of what you’re editing and the playback, with the two-rotary encoders providing the controls. It has a number of play modes (forward, back, pendulum, ping pong, limit and random). You can limit the no of steps, play certain parts of a sequence, and the visual feedback is quite good. A great feature is the built in quantiser with different scales and modes, including things like whole tone, enigmatic, heptatonic blues etc. You also have random trigger with width control, random CV, internal or external clock selection, random sequence generation and presets. Yes, it has a lot crammed into the package!

My only hesitation with this module is the immediacy of the interface. Like the Expert Sleepers Disting MK3 which lacks the display of the MK4, the Prizma is crying out for a little screen, the issue being that with all the functions and sub-menus there’s a risk of you not knowing exactly where you are. Note that the LEDs do provide visual feedback on what’s being edited, there’s just a bit of a learning curve.

Despite being a pretty cool module, I’m going to pass on it for this project. I do love the features, particularly the quantising options, however I’m not convinced I’ll enjoy the interface which is a personal thing. I’d love to see a little OLED on this to support the LEDs, and either way I’d encourage people to look at the Doboz modules as there’s another interesting touch plate keyboard which runs of an Arduino NANO.

Manufacturer’s link: http://doboz.audio/PRIZMA/

Final selections

Sequencer for bass shortlist

• GMSN! Pure Sequencer
• RYO VC Sequencer and Trig Expander
• Razmasynth VIII
• Synthrotek Sequence 8
• Division 6 Dual Mini Sequencer
• Cavisynth SEQ-UFD
• Shakmat Modular Bishop’s Miscellany
• Music Thing Modular Turing Machine

Sequencer for chords shortlist

• Shakmat Modular Bishop’s Miscellany
• Mutated Yarns
• Ornament & Crime

Final selection – Module 1

Selecting sequencers has been one of the most difficult and time consuming tasks. Apart from providing different pitches over time, the functionality and interfaces of sequencers can vary dramatically. I imagine that people’s favourites would come down to not only application but how your brain is wired.

This brings me to my favourite module, the Bishop’s Miscellany. Because of it’s record function it lets you record sequences as played so you can skip steps and sequence more of a groove. It’s also the most fun module due to it’s A/B function, shift and step limit via a knob (rather than patching a gate to reset), allowing you to really play live with a sequence. The demos also show use of some touch controllers which are desirable, but can I DIY them including the faceplates? That’s for another post, and despite that question I’m happy to have the Bishop’s Miscellany module is my first selection.

Final selection – Module 2

The question now is whether I add something else to do chords or bass? It’s easier to look at the chords as there’s less options. So it’s the Yarns vs the O&C. Despite the Yarns winning points by having an arpeggiator and a MIDI interface, I find the O&C has a better user interface, plus its non-sequencing functions. Also potentially being the only display on my synth, the OLED of the O&C is a lot nice than the old school 8-segment LED of the Yarns.

So, do I ignore all the simpler bass sequencers for the O&C? The answer is yes. The cool thing about selecting both the Bishop’s Miscellany and the O&C is that they both do chords as well as standard sequencing, so there’s flexibility and I can switch between them. The O&C is also a good platform to expand my synth in the future as more apps are released. I also get an army of other functions under the hood to expand my options if I run out of things like LFOs or envelope generators.

But wait there’s more

One last thought. Both the O&C and the Bishop’s Miscellany typically need CV to drive the chord generator and recording functions respectively. So does it make sense to add a third sequencer just for this? Perhaps. The Bishop’s Miscellany demonstrates you don’t need one, especially if you have quantised touch controls. But how am I going to get the O&C to generate chords if the Bishop’s Miscellany is used for something else?

At this stage I think it’s best to wait and select the MIDI interface and quantisers, which will be the next post in the series, along with control options such as capacitive touch controls, wheels, joysticks and anything else useful I can find. Then I may add a simple sequencer if I feel it’s required.