Dave Smith may have just created the analog keyboard to beat.

The Mopho x4 is a new, bigger sibling to the Mopho keyboard – itself a nice, cute, yellow analog monosynth. The x4 takes that synth, quadruples the voices so that you get polyphony, and adds more-playable controls and functionality. You get a nice complement of hands-on controls, but you also don’t break the bank: US$1299 is the list.

Dave Smith himself shows off the creation in a video — he, the father of MIDI and some of the best-loved synths over the years (from Sequential to his own DSI). And Dave, while unassuming as always in his presentation style, gets some great sounds out of the thing.


  • 4-voice polyphony
  • Each voice has two analog oscillators and two sub-octave generators
  • 2- or 4-pole Curtis low-pass filter
  • Three 5-stage envelope generators
  • Four LFOs
  • Re-latchable arpeggiator
  • 16 x 4-step sequencer. The sequencer is actually really intriguing, analog-style in design, though fairly complex and deep. Most likely, this is the one part you will program from software, not the front panel (see the bundled, free editor in the vid). Not only can you create elaborate patterns, but you have a range of possible modes and routings.
  • 20 modulation sources, 50 destinations
  • FM filter modulation, feedback path
  • In addition to being able to route the LFO to the oscillator, there are “tuning drift” controls for creating some random pitch fluctuation (since the digitally-controlled analog oscillators are always in tune!)
  • 100% analog signal path… okay, yes, all-analog can become a sales gimmick (and DSI has built some great instruments without the analog signal path), but the important thing is, knowing what the Mopho sounds like, this is a terrific sonic architecture.
  • 44, semi-weighted keys and velocity and aftertouch, plus full-sized pitch and modulation wheels.
  • USB, MIDI, CV, and a full range of audio and pedal jacks

You can also chain this with other DSI instruments. And it’s made in the USA, in San Francisco. See the video for a sense of what this looks like:

So, let’s get this straight:
It’s analog.
It’s polyphonic.
It’s fully programmable.
It’s still priced like many digital synths.

Clarification: The only real bad news is, you could achieve more interesting multi-timbrality by chaining multiple analog synths; not everyone wants big, stacked sounds. But you do get some flexibility here. From the documentation, you can operate either polyphonically (and chain together more DSI stuff for added polyphony), or switch to a unison mode:

Unison On/Off—When on, Mopho x4 behaves like a monophonic synthesizer and only one note will play at a time. Unison Mode—Sets how voices are allocated and tuned when unison is on.

[Unison modes]
1 Voice: Classic, two oscillator, monophonic mode
All Voices: All four voices in unison
AllDetune1-3: All four voices in unison with increasing levels of detuning among the voices

Yep, I want to try one. After all those intriguing keyboards we’ve seen this year, having a 4-voice, playable analog synth with this sonic range and functionality to me makes the Mopho x4 stand out. But stick around for a hands-on review when we can get one over to Germany or do a shoot in San Francisco.