ASM Ashun Sound Machines Hydrasynth Keyboard Synthesizer, 49-Key

Get experimental, expressive sounds with the Hydrasynth from ASM. Its deceptively simple interface lets you unlock a world of tonal and textural variations.

The ASM HYDRASYNTH keyboard is both a sound designer's dream synth as well as a performing musician's ideal. The sound engine is designed for maximum flexibility. At the same time, ASM designed the user interface in a way to allow you to edit the patch quickly with a minimal amount of paging and many workflow shortcuts.

Take a tour of the Hydrasynth:

Utilizing an advanced wavetable synthesis engine, 3 Oscillators, dual Wave Mutators and 2 filters that can be configured in series or parallel, the tone generating capabilities are unmatched.

As for the performance capabilities, The HYDRASYNTH keyboard has a proprietary Polytouch keybed that offers polyphonic aftertouch over each note, giving you the type of expressive control found only in certain vintage synths.

Add to this a 4-octave ribbon controller and ergonomically designed pitch and mod wheels and you have expression and control that is not equaled in any other hardware synthesizer on the or ever.

Polytouch Keybed

The ASM Polytouch keybed allows not only the standard velocity and aftertouch found on other keybeds but also fully polyphonic aftertouch.

In recent years companies have been trying to find ways to give the keyboard musician more ways to better express themselves. The problem is that their solution is almost never a keyboard, so you have to learn a new technique to play them.

The Polytouch keybed features a high quality, standard sized keys, so you can start playing it instantly. read more


The tone generation capability is the heart of any synthesizer. The 3 oscillators allow you to choose from a selection of 219 single cycle waveforms.

Wavemorphing is a feature usually found on synths with preset wave tables. Creating user wavetables is arduous or downright impossible. Unlike most wavetable synths, ASM oscillators 1 & 2 have a WAVELIST mode. This mode allows you to pick and choose 8 waves, from a bank of 219, arrange them in the order you want, and then morph from one to another.


Oscillators 1 & 2 are routed into the MUTATORS. Mutators allow you to modulate, bend and sculpt the sound in new (and old) ways. Each MUTANT allows you to choose from the following processes:
- FM Linear - for making classic FM sounds. Choose multiple FM sources, including external inputs.
- Wavestack - creates 5 copies of the incoming sound and allows you to set a detune amount.
- Hard Sync - This gives you those classic hard sync sounds. Try hard syncing a morphing wavetable for some fun.
- Pulse Width - This will pulse width modulate ANY input sound.
- PW - Squeeze - This is a different form of pulse width mod that creates a smoother sound.
- PW-ASM - this mode divides the incoming wave into 8 slices and allows you to set how much pulse width mod will happen in each section.
- Harmonic Sweep - this will sweep the harmonics of the incoming sound.

The Mutants can also generate their own waveforms in both FM and Sync modes so that you do not have use another oscillator....Of course the routing is flexible so you can choose the other oscillators as mod sources if you like.

Mixer/ Filter Routing

The 3 Oscillators are fed into a mixer along with the Noise generator and Ring Modulator. The Mixer allows you to mix levels as well as pan the input source. There is a balance control that allows you to choose how much signal of each source is routed to filters 1 and 2. The filters can be set to be parallel or series for ultimate flexibility.


If oscillators and tone generators are the heart of a synthesizer, the filters are the soul. The Hydrasynth has two filters that can be configured in series or parallel. The first filter has 11 different filter models, giving you multiple options for tailoring your sound. The second filter is a 12db per octave has a continuous sweep from Low pass to bandpass to high pass, similar to the way the classic SEM filter worked.


5 Low-Frequency Oscillators...YES, 5. Much like the sound engine, the LFOs are not ordinary by any means. The Hydrasynth LFO's feature a STEP mode that allows you to create patterns with up to 8 steps. Having 5 mini step sequencers gives you an amazing amount of possibilities for further shaping your sound. Of course, there are also 10 standard waveforms to choose from. The LFO's all have delay, fade in, 3 triggering modes, smoothing, start phase, one-shot mode so that they can act as envelopes and BPM sync.


5 DAHDSR Envelopes......YES 5. An advanced sound engine needs plenty of modulation sources. The Hydrasynth's 6 stage envelopes feature Delay, Attack, Hold, Decay, Sustain and Release stages. The time settings for the stage can be set in seconds or in time divisions, giving you envelopes that play in sync to your song.

You can also loop the envelopes to create LFOs whose shape can be voltage controlled in the modulation matrix.

Modulation Matrix

The modulation capabilities on the Hydrasynth are endless. With 32 user definable modulation routings, you will have plenty of ways to use the 29 modulation sources and 155 modulation destinations. Almost everything in the synth engine can be a modulation destination including the effects and arpeggiator. The Modulation matrix points themselves can also become modulation destinations. Modulation sources & destinations include the CV Mod In & Out jacks as well as MIDI CC's.


The arpeggiator allows for standard note arpeggiations but also has a phrase arpeggio built-in. Parameters like RATCHET and CHANCE will generate other rhythmic patterns with some randomness to add life and spontaneity to your performance. You can also modulate most of the parameters in the arpeggiator so imagine using LFO's, Envelopes, Polyphonic Aftertouch or the Ribbon controller to modify your arpeggios in real time.


There is the standard MIDI and USB/MIDI interfaces on the synth but ASM goes deeper and allows the use of CV/GATE interfaces for connecting to the modular world. It supports the standard voltages for Eurorack modulars as well as some of the Japanese Volts>HZ products. The MOD in and outs allow for modulation from DC to full audio ranges, expanding your modulation capabilities.

Main Controls

The Main system controls are where you navigate your patches, configure system settings and see parameters like the envelopes, waveforms, filters in the OLED screen. Init and Random buttons will allow you to initialize or randomize a complete patch or specific modules with a press & hold + module select button. Pressing the HOME button returns you to navigating patches in a simple and easy way.


The patch MACROS are designed to allow the user deep control over the engine in live performance. The 8 assignable encoders and buttons can each be routed to 8 destinations. Complete sound transformations can take place with the press of a button or turn of a knob.


The Hydrasynth comes with 5 banks of 128 patches in total. ASM hired some of the best patch designers around to create the 256 factory patches.
Finding the patch you want and searching the library is made easy with our BROWSER. Our PC/MAC based Patch Manager plug-in also allows easy moving of patches to create your favorite order as well as load in new patch libraries in the future.


The effects chain goes beyond the typical ones found in other synths. Pre-effects and post-effects give you some unique ways to process your sound. The delays and reverbs were modeled on some of the most popular effects on the market. The effects are the perfect way to complete your sound, in the box.
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- Metal Chassis:
- Steel top and bottom
- Aluminum side panels

- PolyTouch Keybed:
- Polyphonic aftertouch
- Velocity

- 4 octave (67 cm, 26.4") Ribbon controller:
- Pitch bend mode
- CC control mode - modulation source
- Theremin mode - triggers envelopes and plays pitch - Continuous pitch or choose from multiple scales

- Banks: 5 banks of 128 patch memories

- CV gate input and outputs:
- Support multiple CV/GATE standards
- CV
- 1v per octave +/-5V
- 1V per octave 0-10V
- Hz to Volts +/-5V
- Hz to Volts 0-10V
- Gates
- V-trig, S-trig
- 3V, 5V, 10V
- Mod In/Out range
- +/5V, 0-10V, 0-5V, 0-1V
- Clock in and out
- 1PPS, 2PPQ, 24PPQ, 48 PPQ
- Clock Voltage - 3v, 5V, 10V

- MIDI IN/OUT/THRU: Voice overflow mode for expanding voices with another Hydrasynth

- Expression pedal input: Yes

- Sustain pedal input: Polarity sensing input\0x200B

- DC input jack: Yes

- USB port: Supports USB MIDI In/Out

- Dimensions: 80 x 35 x 10.3 cm (31.5 x 13.78 x 4.05 inches)

- Weight: 10kg (22.05 lbs)

- Voices: 8 Voice Advanced Wavetable synthesis

- 2 Wavemorphing Oscillators:
- 219 single cycle waveforms
- User wavetables - 8 user selectable 'wavelist' per osc to build user wavetables
- Every osc and patch can have its own user wavetable
- WaveScan parameter for modulating through wavetables.
- Keytracking - 0-200%
- +/- 3 octave tuning range

- 1 fixed Wave OSC:
- 219 single cycle waveforms
- +/- 3 octave tuning range
- Keytracking - 0-200%

- Dual Mutators per oscillator:
- FM - Linear FM
- Selectable Modulator source
- Built in Sine & Triangle, OSC1, OSC2, OSC3, Mutators A, B, C, D, Noise gen, Ring Mod, External Mod 1&2 input.
- WaveStack - Generates 5 detuned waves from input source. Detune amount.
- Pulse Width Mod - Adjust pulse width of ALL waveforms.
- PWSqueeze - Compresses the center section of the waveform. Differnnt type of PWM
- PW-ASM - 8 User adjustable wave squeeze/stretch points.
- Hard Sync - gives that classic sync sweep sound.
- Selectable Sync input source.
- Harmonic Sweep - will scan through the harmonics of the incoming sound.
- Dry/Wet mix to blend the original OSC source.

- Noise Generator: White, Pink, Brown noise sources

- Ring modulator:
- Selectable input sources
- OSC1, OSC2, OSC3, Noise, All Mutator outputs, External Mod \0xBD in.
- Depth control

- Sound source mixer:
- Mix the following sources - OSC1, OSC2, OSC3, Noise, and Ring Mod.
- Panning for each source
- Filter routing mix
- Solos for each source (solo status is saved in the patch)

- Two Filters:
- Series or parallel routing
- Filter 1
- 12 & 24db modern ladder (compensated)
- 12 & 24db vintage ladder (uncompensated)
- Threeler HP, LP
- MS20 HP, LP
- Low Pass Gate
- Vocal filter
- Multiple vowel order parameter
- Formant parameter
- Filter 2
- Continuously Variable Lowpass-Band pass-High pass (Oberheim SEM style)

- 5x Low Frequency Oscillators:
- 10 static waves
- Sine, triangle, Square, Saw up, Saw down, S&H, Low random, Noise, Pulse width 25%, Pulse Width 12.5%.
- Step Wave - 8 steps that the user can set (like a step sequencer).
- Step smoothing
- Step glide
- Clock sync
- Starting phase
- Start delay
- Fade in
- Master output gain
- Trigger modes - mono, poly, free
- One shot mode

- 5x Envelope Generators:
- 6 stage DAHDSR envelopes
- Delay, Attack, Hold, Decay, Sustain, Release
- Slope curves for ADR stages
- Variable from full exponential to full logarithmic
- Tempo or Time option for setting length of each stage.
- Looping of AHD stages for creating LFO types of modulations.
- Trigger modes - Legato, Reset, Retrigger

- Matrix modulation:
- 32 slots for source-destination mod routings with amount
- Modulation matrix slots can be mod destinations

- 8x Macro knobs and buttons: Each macro knobs allows positive and negative of up to 8 destination controls

- Arpeggiator:
- Arp parameters can be modulation destinations.
- Modes
- Up, down, up/down, Up&down, random, note order, chord, pattern
- Octave
- Range, 1,2,3,4
- Play order
- Up, down, up/down
- Swing
- Gate time
- Ratchet - repeats notes
- Chance - sets how often the ratchet takes place.

- Pre-effects - before Delay and Reverb: Chorus, Flanger, Rotary, Phaser, Lo-Fi, Tremolo, EQ, Compressor (with side chain)

- Delay: Tape, Ping-pong, Analog, PitchShift, Reverse, Filter delay

- Reverb: Room, Hall, Shimmer, Cloud, DarkSpace

- Post-effects - after Delay and Reverb: Chorus, Flanger, Rotary, Phaser, Lo-Fi, Tremolo, EQ, Compressor (with side chain)

- Dimensions: 80 x 35 x 10.3 cm, 31.5 x 13.78 x 4.05 in
Dimensions and Weight in Packaging
Base Item
Shipping Weight: 33 lbs
Shipping Dimensions: 38 x 22 x 8 in
Manufacturer Part Number (MPN): HSKB

For support or warranty questions, please contact the manufacturer:

Reviewers gave this product an overall rating of 5 out of 5 stars. (3 ratings)
Submitted February 17, 2020 by John Hubbard in Denton, TX

"A sound lab with keys"

Overall: 5 out of 5 stars
(see rating details)
Verified Customer zZounds has verified that this reviewer made a purchase from us.
This think exceeds my expectations. Pretty much anything you can think of can be dialed in. It's not as immediate like most synths but learning it's depths can yield surprising results. The build is very reliable and sturdy. Encoders are smooth and positive and displays are crisp and insightful. There is a great FB community that regularly has the ASM engineers visit to listen to users and offer help when needed. This is definitely a synthesizer for sound designers and synth players.

Musical Background:

Hobby player, producer, programmer

Musical Style:

Electronic, Synthpop, Industrial, Progressive, Rock
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