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Page 2: ASM Hydrasynth

Digital Synthesizer By Paul Nagle
Published May 2020


Perhaps the greatest source of inspiration, at least if you enjoy modular-level craziness without effort, is the Random button. You can randomise individual modules or the entire patch, the latter generating far more usable sounds than it has any right to. In my first few minutes with the Hydrasynth, I hit the Random button and turned a plain vanilla synth pad into a chirping, echoing rain forest. Since then I've used it to summon bleak industrial wastelands, a thousand angrily bombilating insects and the dripping of water in a vast cave. Splendid!


The effects are routed in a fixed configuration, the flow illustrated on the panel. Both Pre- and Post-FX feature Chorus, Flanger, Rotary, Phaser, Lo-Fi, Tremolo, EQ and Compressor. In between are a delay and reverb in series, the delay offering times of up to three seconds and types including reverse and tempo sync. This passes into a 90-second reverb with four types (Hall, Room, Plate and Cloud) and a freeze option to sustain indefinitely. The reverbs ooze quality and Cloud quickly established itself as a go-to for spacious pads and atmospherics.

The rest are equally good. The compressor features a side-chain input, which is quite rare in synths generally. You can choose whether to duck the signal according to the tempo, to the action of the Tap Tempo button or by either of the Mod inputs. Feed a kick into one of these and you can pump to your heart's delight.

The phaser is rich and usable, the chorus adds subtle warmth — progressing to full-on ensemble — and the flanger is deliciously whooshy. Should you need to interfere with the Hydrasynth's clarity and polish, the Lo-Fi effect has filters of various types, plus downsampling. Or if you simply require some fine-tuning or finishing off, the EQ is a valuable addition.

To satisfy users intent on applying analogue qualities to their digital synths, ASM have added a 'Warm Mode'. Located in the Voice menu, this applies a low boost and high-end roll-off comparable to that of analogue synths. In the same menu are 'analogue feel' and random phase — more tools for toning down the precision. A sixth LFO is there too, reserved for vibrato.


The arpeggiator occupies a fair chunk of panel real estate, and has a selector for choosing up, down, random and other modes. Of partial interest to those pining for a sequencer are 'Order', in which the notes are played back in the order entered, and 'Phrase', which serves up one of 64 (preset) phrases. The arpeggiator is further spiced up by Ratcheting — step repeats — with a Chance parameter to determine the likelihood of repeats occurring.

Right now, if you turn on the arpeggiator any currently sounding notes are silenced, which is a bit of a buzz-kill. Otherwise, it's a nice implementation that's capable of refreshingly unpredictable results if you modulate its parameters. It's even possible to step through it manually using the Tap Trig function, which is very cool.The desktop version's rear-panel connections are heavily recessed to allow rackmounting. The connections are identical for both models, except that the headphone port is found on the front edge of the keyboard version.The desktop version's rear-panel connections are heavily recessed to allow rackmounting. The connections are identical for both models, except that the headphone port is found on the front edge of the keyboard version.


A patch really comes to life with well-crafted Macros: user-defined roles for the encoders and buttons. With up to eight parameters stacked on each encoder, it's an incredibly powerful way of making changes to multiple parameters at once.

When assigning a Macro, you can work with all the usual modulation destinations, plus arpeggiator and effect parameters and even the CV outputs. The encoders can transmit MIDI CCs, too, although these are tossed in amongst the general NRPN output. To remind you what's going on, each Macro can be named.

This can be hugely rewarding, even if sometimes programming every Macro to your satisfaction can take a while. Although ASM have supplied some preset names, I'd have appreciated an option to copy Macro data from other patches or templates. During the review period, I started maybe 70 or 80 patches, but have yet to flesh out more than a handful of their Macros.

Desk/Rack Model

Compared to the keyboard version, the Hydrasynth desktop fares pretty well. Apart from the obvious differences, the desktop lacks some dedicated knobs and the Glide and Chord buttons, of which only the latter indicates lost functionality. The Chord button is a neat tool for capturing a bunch of notes to be played as one-finger chords, complete with transposition, so it would be nice if this could be added to the desktop too, via a new button combination.

The desktop version drops the keyboard in favour of 24 'Polytouch' pads.The desktop version drops the keyboard in favour of 24 'Polytouch' pads.

Whereas the desktop module has a single headphone jack, the keyboard has a pair of them — quarter-inch and mini — and a volume control. Unusually, the desktop ships with 19-inch rack adaptors; at last, a company who understand there's no such thing as infinite desk space! With racking in mind, the module has the jacks and power switch deeply recessed (the supply is external). Both models have expression and sustain jack inputs.

Those inputs, plus the Desktop's 24 rubber pads, make it a viable proposition for stand-alone programming, jamming and even performing. The pads send velocity and polyphonic pressure. They can be tuned to a variety of scales and operated in either chromatic or fretboard layout. In chromatic mode, black keys are red, white notes are blue and root notes are yellow — something you soon adapt to. However, the scale text is printed in dull orange, making it hard to see in low light. That said, you quickly memorise the positions of your favourite scales. At the time of review, the selected scale is not stored over power cycles, or per patch, which feels like an opportunity missed.

My only misgiving is that the pads aren't responsive enough for all playing styles. For expressive poly-pressure performances, they work well enough, but you must hit them quite deliberately when playing percussively as light strokes are often missed. Hopefully some ability to tailor user responsiveness will be added in the future.


You don't need chops like Vangelis to appreciate poly pressure. Even for we lesser mortals, playing the Hydrasynth is a wonderful experience, after which conventional keyboards feel crudely limited. Whether you're morphing waveforms, attenuating Mutant levels or varying modulation speeds, those subtle, per-note nuances can really breathe life into a performance. Similarly, the ribbon is a superior way of bending pitch — and some of its other modes are just as sweet, not least the ability to kick off a keyboard drone then play an eerie Theremin solo over the top. This is a hugely enjoyable synthesizer to play, and it might be argued that a reduced number of controls plus well-implemented Macros can lead to more focus. Even so, I often wished for simultaneous access to the filter and amplifier envelopes — preferably quicker than it would take me to program up those precious Macros.

The Hydrasynth's sound is a tough one to pin down, because it is so wide-ranging. A digital synth with a clear, bright modern sheen, it has a solid bottom end and can slip easily into a mix. Credible analogue emulations are within its grasp but, for me, its greatest strength is in modular-like complexity. True, there's a temptation to keep tinkering and refining an idea forever, but instant gratification is available too, at a press of the Random button.

Arpeggiation was clearly a design priority, even if some of us would have been content with a simpler implementation as long as it left room for an equally simple sequencer. Nevertheless, the arpeggiator is funky and more hands-on than most, turning wildly eccentric when modulated.

Before I started this review, I expected the keyboard version to be the optimum choice due to its ribbon, keyboard and physical controls. While these are undeniably major attractions, the module's pads and compact format offer the freedom to jam or program patches without an external controller. Whichever model appeals, the Hydrasynth is a seriously impressive opening salvo from a fledgling company. Hopefully, it heralds a more expressive future for synthesis. Hail Hydra!


The Novation Peak and Summit both have analogue filters and luxurious control panels, and higher price tags accordingly. Both respond to polyphonic aftertouch, but this must be sourced externally. Another option would be to line up for an Expressive E Osmose, which is currently in development and incorporates 3D control in every key, plus the sound engine of the EaganMatrix. However, if five octaves are a minimum requirement (and you can't find a second-hand Gem S2 or S3), you'll need to keep waiting.

In the meantime, you might do what I did a few years ago and put together a CME Xkey37 controller, a stand-alone ribbon (I picked the Doepfer R2M) and a synth that responds to poly pressure, like the Waldorf Blofeld. It's not elegant and you need some means of merging the keyboard and ribbon data, but it works.

Funky Ribbon

The ribbon can be used for pitch-bend, as a modulation source or in a unique 'Theremin mode'. In the latter, one of the eight voices becomes a dedicated Theremin voice, its volume articulated separately via the mod wheel. You can choose the pitch resolution — two, four or six octaves. By choosing four you can play the ribbon almost as an Ondes Martenot player would, the pitch corresponding to the keys below.

Vibrato can be achieved by wobbling a finger, and if you set a key and scale, you'll never hit a wrong note. The only issue I had was when I swept up to the very top C and sometimes ended slightly flat, even after recalibration.

It's up to you whether to work with the ribbon's absolute position and map the complete range of a controller over its full length, or relatively. Relative mode usually felt superior for pitch control, because wherever you touch the ribbon, that point automatically becomes zero. You then move freely up or down the remaining length.


Both models include 3.5mm CV and Gate connections. These aren't mere afterthoughts but integral to the design, with all the usual voltage ranges and triggering methods supported and up to 10V to play with. Via functionality in the mod matrix you can perform CV inversion and attenuation.

The two Mod inputs are ready to receive voltages from weird or exotic utility modules, but can handle audio levels too. The only route into the mixer is via the ring modulator, but with a little thought it's possible to incorporate a Eurorack module (for example) as a fourth oscillator. The CV outputs allow you to clock a sequencer, play an analogue synth or translate Hydrasynth performance controls or modulation sources into voltages. The keyboard model's Theremin mode can be routed to an external synth using the Pitch and Gate outputs, delivering solos that are entirely independent of notes played on the keyboard.


  • Polyphonic aftertouch, at last!
  • Ribbon control on keyboard version.
  • The module can be played and programmed stand-alone.
  • Flexible synthesizer engine with wavescanning and several unique processors.
  • Good-quality effects.
  • Solid build.
  • Versatile CV/Gate implementation.


  • Some will reject the keyboard as too short.
  • Desktop would benefit from adjustable pad response.
  • Programming can be dangerously addictive.
  • External power supply.


A synthesizer that justifies its initial hype, offering a fresh take on wavetable synthesis and a superior modulation and effects section. The keyboard's polyphonic aftertouch and ribbon controller are very welcome indeed, while the module's self-contained nature has its own charm.


Hydrasynth Desktop £799, Hydrasynth Keyboard £1299. Prices include VAT.

Hydrasynth Desktop $799, Hydrasynth Keyboard $1299.