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  • Electro-Harmonix Mini-Synthesizer App

    By Phil O'Keefe |

    Electro-Harmonix Mini-Synthesizer App


    A low-cost hardware synth classic returns as an even lower-cost app



    by Phil O'Keefe


    harmonycentralehxminisynthappleader-4c081346.jpg.13be0390a9af2a394eb98cbba6ad6ea8.jpgMention Electro-Harmonix, and most people think "guitar and bass effects pedals." That's not surprising, considering they were pioneers in the field and have been making pedals for decades. But pedals are not all they make, and in fact they have a long history of making synth-related products too, such as the recently reissued (and reviewed) Crash Pad and Super Space Drum percussion synths that were developed in the late 1970s.


    Another synth-related product from the same era is the original EHX Mini Synth. Built into a compact metal case with a 25 note membrane "keyboard," this single-oscillator synth was one of the least expensive ways to get a keyboard synth. Now Electro-Harmonix has also reissued this classic, but unlike the recently reissued hardware drum synths they've done so in software form - let's get to know the Electro-Harmonix Mini-Synthesizer app.



    ehx-mini-synthesizer-main-2be5d521.thumb.jpg.37f23759c86040d80940b674def05c1f.jpgWhat You Need To Know

    • The Electro-Harmonix Mini-Synthesizer app is a faithful software recreation of the original hardware EHX monosynth from 1980. It's currently available for iOS devices (running iOS version 8 or later) - including iPads, the iPod Touch and yes, iPhones too.


    • The interface looks very similar to the original, with a reverse-color virtual keyboard sitting below various "slide"-style controls with colored knobs that are grouped together in various sections, just as on the vintage hardware synth.


    • Like the hardware synth, the app version is a single oscillator synth, with a virtual version of the original VCO and its pulse waveform.


    • The pulse width can't be changed, but the oscillator does have a pitch control slider and a suboctave (one octave below) can be mixed in for added thickness.


    • Rounding out the Oscillator section, an Octave Up switch can transpose the notes up an octave (including any notes you are playing), and a Tune knob fine-tunes the synth over a +/-50 cent range.


    • The Filter section is the most powerful section of this simple synth. A Phase Rate slider adjusts the phase shift speed, and can give the oscillator's square wave-sounding tones more of a buzzy sound similar to a sawtooth. The corresponding Phase Switch turns the effect on or off.


    • Filter Start and Filter Stop sliders let you dial up the start and ending frequencies of the filter sweep, while the Rate slider controls how fast this occurs; it maxes out at about two seconds.


    • Three more switches round out the Filter section. A Q switch adjusts the filter's bandwidth from fairly broad to a narrower and more resonant setting, while the 2X Filter switch changes the audio routing through the filter, which is either in parallel or in series.


    • The Retrigger switch is new and can cause the Filter to retrigger with each key played, even if another key is being held down.


    • Unlike the first hardware EHX Mini-Synthesizers, the EHX Mini-Synthesizer app has Delay and Reverb effects onboard, with an on / off switch for each. The order of these two effects can be swapped around, so it's possible to run the delay into the reverb or vice versa.


    • The Delay section includes Time, Feedback and Blend sliders. Maximum delay time is about 2 seconds. The Delay will self-oscillate (or at least infinitely repeat) when the Feedback and Blend are maxed out.


    • The Reverb offers control over Amount, and the Blend of the wet and dry signals. The Amount slider seems not only to adjust the reverb effect level, but also the length of the tail grows longer at higher settings. Touching the Reverb label above the slider opens a selection box with Plate and Reverse options.


    • A Volume slider adjusts the app's overall volume level.


    • There are some other differences between the app and the original hardware synth. For example, the keyboard isn't limited to the original hardware's 25 keys. A Horizontal Slider just above the keyboard lets you slide the keyboard left or right over a full eight-octave range.


    • Furthermore, the keyboard layout is user-customizable and very playable, which isn't aways the case with iOS virtual keyboards. For example, if you want to play in G major, you can edit the "Modern" keyboard layout to remove the F, G#, A#, C# and D# from it entirely, leaving only the notes of the G major scale.




    • A cool "Ribbon Controller" (the black and white striped area directly above the virtual keyboard) is to a conventional keyboard as a fretless bass is to a fretted bass. It also works in conjunction with the virtual keys; you can play a note on a key, then slide your finger up to the ribbon and finally, slide to the key on which you want to end.




    • While the original Mini-Synthesizer was strictly a monosynth, the app gives you the option of running it either mono or with four-note polyphony.


    • 22 presets are included, and you can create and save your own too. How many? You're really only limited by your device's memory, so… quite a lot, but don't expect me to try to count them for you!


    • As you'd expect, inter-app audio and Audiobus are supported, and the Mini-Synthesizer also has a virtual MIDI input (so you can use an external MIDI controller instead of the virtual keyboard), and offers direct connectivity to DAW apps as a audio input.



    • For those using an iPhone 6s or 6s Plus the keyboard actually supports aftertouch!





    • I was unable to get the app to work with iOS 8 on an iPad mini 2. The app would load and seemed to function properly but there was no sound. Updating to iOS 9.3.3 cleared up the issue for me.


    • An Android version is in the works but won't be available until October 2016.


    • The "Classic" keyboard layout is static and cannot be user-modified. Also, the virtual keyboard's inverted color scheme is not flippable to the more familiar arrangement.





    Let's face it - this isn't the most powerful synthesizer ever designed, and if you're looking for something complex and complicated you'll want to look elsewhere. But this is a fun recreation of a vintage classic, with some useful added functionality. In particular the configurable keyboard is lot of fun and far more playable than what you'll find in most apps, and the onboard reverb and delay effects are solid additions that add quite a bit to the sound manipulation capabilities. While I'm sure some users will prefer to run the Mini-Synthesizer through their hardware effects pedals, the onboard effects are great to have for on-the-go use, and unlike hardware pedals, their settings get saved with any presets you create.



    The original EHX Mini-Synthesizer was a "cheap and cheerful" way for people to get their feet wet with subtractive analog synthesis, and the new Electro-Harmonix Mini-Synthesizer app maintains that tradition admirably. It's high on the fun factor, and not at all challenging to use. At five bucks or less, it's a no-brainer app purchase for musicians everywhere, as well as anyone who is interested in learning about synthesis or just wants to have fun making some noise.  -HC-


    Join the discussion






    Electro-Harmonix Mini-Synthesizer App ($2.99 for iPhone / iPod, $4.99 for iPad)


    Electro-Harmonix Mini-Synthesizer product web page   




    You can purchase the Electro-Harmonix Mini-Synthesizer app from the



    Apple App Store (iPad)    


    Apple App Store (iPhone)    

















    Phil O'Keefe is a multi-instrumentalist, recording engineer / producer and the Senior Editor of Harmony Central. He has engineered, produced and performed on countless recording sessions in a diverse range of styles, with artists such as Alien Ant Farm, Jules Day, Voodoo Glow Skulls, John McGill, Michael Knott and Alexa's Wish. He is a former featured monthly columnist for EQ magazine, and his articles and product reviews have also appeared in Keyboard, Electronic Musician and Guitar Player magazines.  

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