• 8-voice Polyponic Wave Morphing Synthesizer
  • Incredible Cost Performance

ASM (Ashun Sound Machines), a new brand on the scene, has released a new hardware synthesizer called the HYDRASYNTH, which comes in 49-key and desktop module versions.


The HYDRASYNTH is a synthesizer loaded with the latest technology, with both a fantastic engine system and sound. Not only that, it also has a very easy to use layout and operation is a breeze, but we’ll get to those later.

The bottom line here is that the biggest feature of this synth is something you don’t even see on high-end synths or controller keyboards: it has polyphonic after touch.

Polyphonic Aftertouch


Of course, most synthesizers come with aftertouch as a standard feature. Even so, this kind of “normal” aftertouch works very differently from polyphonic aftertouch.

For example, say you assign filter cutoff frequency to be controlled by aftertouch, and then play a chord.

With the keys of the chord held down, even if you press down harder on just ONE of any of those keys, which in itself is activating aftertouch, the filter cutoff will be applied to ALL of the keys in the chord. In this way, “normal” aftertouch affects the entire set of keys being played no matter which key (or keys) actually are getting aftertouch input.

Having said all that, we don’t think most people will feel that there’s anything out of the ordinary with that. However, this is what has been considered the norm as far as velocity touch and aftertouch sound control. We’re used to this as being the way things are.

Polyphonic Aftertouch

Polyphonic aftertouch was first seen on vintage, top-tier, polyphonic analog synthesizers like the wel-known Yamaha CS-80. Such synths offered a degree of expression that was much higher, and you can hear the results in many recordings and productions.

Possibly the best example of this is Vangelis’ work on the Blade Runner soundtrack.

At ASM, they’ve re-created polyphonic aftertouch in the form of their own POLYTOUCH™ Technology.

As the pressure data from each individual key played must be processed, resulting in some complex number crunching, this is a feature we haven’t seen very much at all in the synthesizer market. It’s no mistake that ASM are pushing polyphonic aftertouch as a huge selling point of this synthesizer, and the sound of it packs quite a punch.

Sound Engine

Fundamentally, the 8-voice sound engine has three oscillators featuring ASM’s original Wave Morphing Synthesis Engine, which offers 219 single cycle waveforms.

OSC 1, 2, and 3 allow the user to select from one of the 219 single cycle waveforms. OSCs 1 and 2 offer a Wave Scan (Wave List) mode in which a list of eight waves can be set, and via a modulation source each single wave can be morphed, which provides for a very seriously flexible oscillator mode.

The HYDRASYNTH also offers an oddly named modulation function. On the front panel you can find it, labeled as “MUTANT 1~4.” The name of the connected function being the Mutator, which lets you modulate the waveforms in very minute ways.

MUTANT 1, MUTANT 2, MUTANT 3, MUTANT 4 offer four selections:

  • FM-Lin
    Creates a classis FM sound. An external signal cource can also be connected and selected for complex FM modulation.
  • Wavestack™
    Stacks five copies of the selected waveform for a complex unison sound. Each can be detuned, so some VERY thick sounds can be created here.
  • OSC Sync(Hard Sync)
    This is the classic sync sound. When combined with wavetabel morphing, extremely complex sounds can be made.
  • PW-Orig(Pulsewidth)
    Modulates the pulsewidth of the selected waveform.
  • PW-Sqeez(PW Squeeze)
    Offers a smoother PWM than the standard variety.
  • PW-ASM
    Cuts the selected waveform into eight slices, and can modulate the pulsewidth of each slice individualy.
  • Harmonic(Harmonic Sweep)
    Adds harmonics to the selected waveform.

The Mutator also offers flexible internal routing, for feats including finely adjusting or distorting the sound, reversing the sound, and so on, for virtually endless possibilities.

Of course, it’s also possible to add noise or apply ring modulation. The noise generator can produce white, pink and brown noise.

Dual High-spec Filters

The HYDRASYNTH has two filters which can be routed in series or parallel.

There are eleven models to choose from, from a brand new type all the way to classic filters.

  • LP Ldr12 12dB Ladder filter
  • LP Ldr24 24dB Ladder filter
  • LP Fat12 12dB Ladder filter
  • LP Fat24 24dB Ladder filter
  • LP Gate Low Pass Gate filter
  • LP MS20 Low Pass filter with an MS-20 flair
  • HP MS20 High Pass filter with an MS-20 flair
  • LP 3-Ler The Low Pass flavor of a boutique modular synth
  • BP 3-Ler The Band Pass flavor of a boutique modular synth
  • HP 3-Ler The High Pass flavor of a boutique modular synth
  • Vowel Vocal formant filter

The filter also offers Drive, so it’s possible to get a thicker sound that has slight distortion.

The fiter is a multimode classic 2-pole state-variable filter. It operates much in the same way as a classic SEM filter, with Low-, Band- and Highpass modes, which can be continually swept through.

LFO and Envelopes

The HYDRASYNTH has five LFOs and Envelopes. With this many on hand, we think it’s pretty much possible to create any sound you have in mind.

The LFO section offers 10 different waveforms, but there is also a Step mode which allows creation of patterns with up to eight steps. If you put all five LFOs in Step mode, some ultra complex, expressive step sequence patterns can be made.

The five EGs are of the DAHDSR variety. Envelopes can be routed to external destinations (devices) via the modulation matrix. They can also be looped and used like extra LFOs.

Modulation Matrix

The HYDRASYNTH’s modulation matrix is easy to edit down to the finest details thanks to the high resolution OLED screen, and being able to see a huge number of parameters all at once.

Different synthesizers handle modulation matrix editing and functionality in different ways, but with the HYDRASYNTH, it really is a piece of cake. Of course, the OLED comes in handy while editing sounds as it shows various parameters, but what really impressed us was that ASM managed to build a synth in this price range that offers the kind of display and interface the HYDRASYNTH has.


The high-res OLED screen displays a huge amount of information, and editing is very intuitive thanks to the inclusion of a high-res rotary encoder, PLUS eight buttons at your fingertips make editing intuitive and very easy. The Module Select buttons for each section are separated, so it’s easy to see exactly where and what you’re doing as the position is clearly indicated.

The HYDRASYNSTH comes with MIDI and USB/MIDI as well as CV/GATE interfacing options. As there is no need for a MIDI to CV/GATE converter, interfacing with the recently popular Eurorack and other modular synths/modules is easy and convenient. It is also possible to control the HYDRASYNTH from CV/GATE equipped modules.

Bottom Line: Sounds Great, Easy to Use

We think that the excellent sound and super ease of use of the HYDRASYNTH easily makes it one of our favorites among recently produced new synthesizers on the market. Having 8 voices of polyphony is ample enough, but if you stack two units together you can double that to 16. The desktop version comes with 24 pads, which can be set to aftertouch or scale modes, so for those of you short on space, the desktop (which can be rack mounted) is a good option.

By downloading and installing the ASM software on your personal computer, you can upgrade the firmware as well as load new presets into the synth, so it’s possible to keep your unit completely up to date.

Demo & Review Video

You can see and hear the big hitting feature of the HYDRASYNTH—polyphonic aftertouch—in our Demo & Review Video. Check for yourself just what the aftertouch on this synth can do, and how it’s different from your everyday aftertouch functionality.

Sales Info (Japan only)


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