Review – PX Apollo from UVI

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UVI delivers another classic analog instrument, in this case by sampling a rare early prototype polyphonic keyboard from Moog that was lovingly reconstructed for this purpose.


by David Baer, Mar. 2017


About a year ago, UVI introduced the first instrument in the PX Prototype Series whose goal was, in UVI’s words, exploring the oft veiled world of unique, fringe and unreleased electronic and acoustic instruments.  The instrument was the PX Apollo, which is what we are going to look at in this article.  Additional instruments in the PX series have yet to materialize, but, as you’ll see, the PX Apollo is an excellent start.

First let’s get a few important essentials out of the way.  PX Apollo runs in the free UVI Workstation but can also run in UVI’s Falcon hybrid synth.  In the latter case, the wealth of programming possibilities of Falcon can be brought into play that profoundly increase the value of this instrument (my own testing was exclusively using Falcon).  PC and Mac are both supported as is both 32-bit and 64-bit operation (64-bit only when using Falcon).  It works with all major DAWs and has a standalone option as well.  Authorization is via iLok account (software or dongle, your call).  List price (and note: sales are not uncommon) is $79 USD.


The background on this instrument is a bit confusing.  It comes from the time period of the roughly 1972 through 1978.  There were several tries at the Moog company in nailing down just what the instrument was intended to be.  Some name changes along the way compound the confusion.  However, for those sufficiently curious, an informative video from the Bob Moog Foundation Archives details that history:

Here are the basics.  There was a great desire in the early 70s for polyphony in synths, but this was a challenge due to the expense and complexity of the circuitry involved.  There was a technique, however, that had been around several decades.  It was involved having twelve high-register oscillators, one for each note of the Western musical scale, and some very clever electronic circuitry that halved the frequency.  So, one top-octave bank of oscillators could feed the remainder of the lower notes on the keyboard.  Lower the frequency of an oscillator output by a factor of two and we get the pitch of one octave down.  Do that again and we get the octave below that … and so on.  The advantage was full keyboard polyphony.

But there were also disadvantages, especially when compared to the range and flexibility of sound production offered by a full-blown synth.  For example, while oscillators could produce waveforms that could be used to create all pitches over multiple octaves, per-note filters of the kind for which Moog synths were famous were not part of that solution.  A special chip was developed (at considerable expense over a three year period) called the Polycom which provided a simple per-key VCA and VCF articulation.  However, only a single filter was on board the instrument, so playing/holding a chord and then playing individual notes retriggered the filter envelope even for the held notes, at least for those presets that used the filter.  This “feature” has not been retained in UVI’s recreation.  On the plus side, the Polycom chip offered the means to implement per-note velocity sensitivity, a rare feature in keyboards of that era.

In any case, the original Apollo (versions of which were also known as the Polymoog Keyboard) offered a fixed number of largely non-programmable sounds with various timbres, which we’ve been calling presets.  The presets were largely “hard-wired” and each had a single characteristic sound.  One could season these sounds with a bit of pitch modulation and could slow the amp envelope attack, but not a whole lot more.

One other feature was on board: a bass oscillator with filter.  One could switch to a mode where the lower notes of the keyboard would produce bass tones (probably monophonic operation for the bass – not sure on that point).

An earlier version of the Apollo prototype line offered ten presets of which one could be selected via a bank of ten buttons.  This was later expanded to fourteen presets and it was from this version of the instrument that the UVI PX Apollo was sampled.  The Moog Foundation video referenced above states that there are only two known Apollo keyboards left in existence.  UVI states that they rebuilt their instrument from the ground up.  Did they discover a third unit and rebuild that?  That’s not made clear.  But one thing is evident: UVI engineers did a masterful and loving job in this rebuild.  The sound is mostly fabulous – clean, clear and yet full of vintage character.


Above is a screen shot of the main PX Apollo panel.  In the center is the bank of preset switches.  What these are is not specified in the documentation, but the original names of the sounds are as follows:

  1. Vox Humana
  2. String 1
  3. String 2
  4. Electric Piano
  5. Piano
  6. Honky Tonky
  7. Clav
  8. Harpsi
  9. Brass
  10. Chorus Brass
  11. Pipe Organ
  12. Rock Organ
  13. Vibes
  14. Funk

These names are adequately descriptive of what sounds to expect … and those sounds are absolutely wonderful.  To my ears, only Vox Humana sounds a tad grungy and perhaps overly “antique”, but maybe that’s exactly what some users will want.  On the whole, just the unadorned preset sounds alone are marvelously musical and the PX Apollo is suitable for a wide range of applications, even if limited to only those preset sounds.

But those preset sounds are not all.  To the right of the preset buttons we see an array of twelve waveforms, one of which is selected via mouse click.  This is used in a second polyphonic oscillator to augment the sampled waveforms.  This second oscillator was certainly something not found in the original.  The two-oscillator capability vastly expands the capabilities of the instrument.  There are limited (but entirely adequate for most situations) independent amp envelope and filtering for both A and B oscillators.  Anyone with a modest knowledge of synth programming will know how to use this panel without needing to read the documentation.  That documentation is pretty light, by the way, but given the simplicity of this instrument (the mostly-intuitive user interface, that is), the manual is largely unneeded.

To the left of the presets is a bass source which, although perhaps not technically a sub-oscillator, can be thought of as one.


The next panel (shown above) is the edit page.  Here again, many of the controls need no explanation.  The Depth and Time controls in the Pitch subpanel govern portamento behavior.  In the Stereo subpanel, the Alt Mode setting pans oscillators A and B apart.  Color is an innovative offering that uses adjacent samples, properly pitch corrected, to impart differences in left and right channels for a naturally wider sound.  Within Modwheel, we have vibrato and tremolo dedicated LFOs, the strength of which can be governed in real time via the mod wheel.


Next we look at the Mod tab.  The top half offers a step sequencer which can control volume, filter cutoff independently for oscillators A and B, and can control pulse width of waveforms in oscillator B.  The bottom half is the LFO, of which there’s only one (but we’re already covered for vibrato and tremolo, so this isn’t that as much a limitation as might be thought).  Once again, the controls are straightforward here and most users will not need a trip to the documentation to know how to use them.


Next is the FX panel.  Do you really need any explanations here?  I didn’t think so.  However, do know that the marvelous FX capabilities of UVI Engine/Falcon are what are behind these, so it should be no surprise that they sound great.


Lastly for tabs there’s the Arp page.  There’s an independent arpeggiator for each oscillator.  A quick audition of presets in the arpeggio preset category will show you immediately what can be done with these.  I’m not normally a big fan of using arpeggiators, but, oh my, what joy the arpeggiator presets in PX Apollo bring!  These were brilliantly programmed by some inspired sound designers, so special kudos to UVI for this particular surprise.

Speaking of presets, take a look at the preset menu to the right.  There are over 150 presets in the factory content that aptly show the range of just what PX Apollo can do.  Fourteen of these are just the original preset sounds.  The rest use oscillator B and/or the bass oscillator for a sound not possible on the original instrument.  There is some seriously good content here.  I cannot imagine any keyboard player who did not find several dozen of these presets that will impart much inspiration.  In looking at the credits, you’ll see that some familiar independent sound designers like Nori Ubukata, Xenos Soundworks and Simon Stockhausen contributed.

So, is PX Apollo for you?  It is affordably priced, has great sounds and much, much range of musical possibility.  There’s really nothing I dislike and nothing major seems lacking.  Of course, if there were omissions, those using Falcon to host the instrument could custom program solutions using all the possibilities Falcon brings to the table.  But even those using UVI Engine to host PX Apollo have plenty of sound manipulation possibilities right in the native user interface.

I must say at some point here that I did experience two occasions in which sound playback became erratic for a brief period.  I was exclusively running in standalone mode, so this was not a DAW issue.  However, the problem periods were brief and not repeatable.  It would appear that UVI has a little work to do (there have been no updates since the initial release), but there’s nothing I found to be a showstopper.

PX Apollo can be purchased directly from the UVI web site using the link below.  It is also available from any number of independent retailers, so you might save a little money by checking around for the best price.

UVI has a good selection of demo audio tracks that can be heard to determine if PX Apollo is right for you.  Find them here:

The PX Prototype series is off to a splendid start.  I, for one, am eagerly looking forward to more offerings in this lineup.  Keep ‘em coming, UVI!



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