Review – Repro-1 by u-he

Print Friendly, PDF & Email



No stranger to vintage hardware analog emulation in software, u-he does it again with a virtual incarnation of the Sequential Circuits Pro-One from the 1980s.


by Rob Mitchell, May 2017


The Sequential Circuits Pro-One was a monophonic analog synthesizer produced during the early 1980s. It was less expensive than its polyphonic big brother; the Pro-5. Even though it was not as costly as some other higher priced synthesizers, it still had a huge sound which was hard to match. Around 10,000 were built, and it had been used by such artists as Depeche Mode, Prince, New Order, and Soft Cell.

Repro-1 is a software emulation of this hardware synth with many added features. Modeled at the component level, this emulation takes on a new level of realism and character. It went through a long period of time in beta as they fine-tuned its many settings. The people at u-he even setup a poll on the KVR website, and they asked the forum members to vote on which filter sounded the best. All of these efforts culminated in the software emulation known as Repro-1. Some of its features include two oscillators, a noise generator, 4-pole low pass filter, a sequencer, effects, and over 500 presets. That’s enough of its background; now let’s check it out in detail.

Repro-1 is available in 32/64-bit VST2, VST3, AU, and AAX for the Mac. For the PC, it is available in 32/64-bit VST2, VST3, and AAX formats. There is also a VST2 version for Linux available. Native Instruments’ NKS is supported as well. For the Mac, you’ll need OS X 10.7 or higher. For the PC, you’ll need Windows 7 or higher. They also recommend a modern CPU.


A Tour of the Facilities


After you start Repro-1 in your DAW, you’ll see the main display. At the top-left are the tabs to navigate to the other sections of the synth: Tweaks, Sequencer, and Presets. I will cover the Tweaks and Sequencer sections later, but I just want to take a look at the Presets screen for now. It has a preset browser with the categories along the left side, the individual presets in the middle, and information about each preset on the right side. Right-clicking on a preset brings up some useful options, such as marking it as a favorite, or as junk. The “Junk” option is for hiding a preset in the list that is displayed. You can also use the left/right arrows at the top of the display to skim through the presets one by one. Over 500 presets are included, and they definitely have a high level of quality in their design. I spent quite a while just browsing through them, and found many useful ones I’d like to use in my own tracks.  If you “Favorite” a preset, it will place a star next to its name. It’s great to have so many varied presets to use right away, but let’s examine how those sounds are put together in Repro-1.

The “Synth” display is what you first see when you start Repro-1. This is where you can make most of the changes to the settings that will be the basis of your own presets. It is a fairly simple layout, so there aren’t too many mysterious settings to figure out here. Towards the middle of the display are the two oscillators and the LFO. The Filter and Envelopes are on the right side, and some modulation settings are over on the left. Along the bottom, you can switch the view from a keyboard to the effects.

For the first oscillator, you have tuning settings for the octave (four octaves), semitone (+/- 12), and fine (+/-20 cents). The waveforms include a sawtooth and pulse. You can choose either or both of those two waveforms, and the pulse can be adjusted using the pulse width control. The two oscillators can also be hard-synced.   The second oscillator has a few more settings available. The tuning and pulse width controls are the same, but it also has triangle waveform that can be enabled. The “LO FREQ” switch will enable a very low frequency mode for the oscillator, so it can then be used as an LFO. Disabling the “KYBD” switch will turn off the keyboard follow for the oscillator.

To the right of the oscillators are the Mixer and Glide settings. You can adjust the levels of the oscillators and the white noise generator from the Mixer. You’re also able to switch from the noise setting to a “Feedback” function, which takes the signal path and feeds it back to the mix. This can give it a dose of extra beefy bass. If you are using resonance in your preset, turning up the Feedback will cut back on the amount of resonance. The Glide settings have choices available to enable legato and re-triggering of envelopes. The “Repeat” function will do just that; it repeats the note you just played at the speed in the LFO/Clock/Key settings. “Drone” is similar to “Hold” on some other synths. If you play a note, it will just sustain that same note forever, or until you hit another note. 

The filter is a 24dB per octave (4-pole) low pass, with standard cutoff, resonance, envelope, and key tracking controls. The filter itself sounds very good, and it can self-oscillate. More settings are available for the filter (and other parts of the synth) on the Tweaks page, which I will get to shortly.

On the right side of the display are the two envelopes. One is for the filter and the other is for the amplifier. These both have standard ADSR (attack/decay/sustain/release) settings you can adjust. Nothing fancy to mention here, but the Amplifier envelope also has an extra control to adjust the volume curve. This was added to Repro-1 as the original hardware synth had a curve side-effect on the amplifier envelope.

The LFO can be synced to the host, and it has saw, triangle, and square waveforms included. Even though this might seem like a small number of choices, you can also combine them together for other possible shapes: saw + triangle, or triangle + square, etc. 

To the right of the LFO are the Clock, Arp, and Sequencer controls. The Clock syncs the Arp, Sequencer, and LFO. Its speed is relative to the DAW’s tempo, and ranges from 8/1 to 1/64. The Arp can be set to Off (note you play will just repeat), Up (notes in a chord will play the lowest note up to the highest) or Up/Down (plays upward and then downward). The “Latch” function lets you hit the first note, which will keep repeating, and then you can manually play other notes on the keyboard. For the Arp to work, you must switch the Sequencer setting to “Play”. The “Record” function lets you play a sequence of notes, which Repro-1 will memorize for you, and then you can play them back afterwards.

On the left are the modulation settings. These let you modulate up to five destinations, and can be either set to “Direct”, or to be controlled by the modulation wheel. The three sources you can use are the Filter Envelope, Oscillator B, and the LFO. The five destinations Osc A Frequency, Osc A Pulse Width, Osc B Frequency, Osc B Pulse Width, and the Filter Cutoff.

In the lower-right are the Perform settings. These enhance the modulation possibilities of Repro-1. There are two sources available, and each of them can be assigned to their own modulation destinations. Some of the sources include Gate, Key Follow, Velocity, Aftertouch, and the Envelopes. You can either right-click on one of the panels to get a list of destinations, or click to drag-and-drop on to a knob, such as a stage in an envelope, or the filter cutoff. Some of the destinations include LFO speed, Envelope stages, Oscillator tuning, Pulse Width, and there are many more.


Tweaks, Sequencer, and Effects


When you click on the Tweaks tab, it brings you to a different view of the synth. It looks like the top panel of the synth has been removed, and it lets you gain access to some extra settings. These other selections you can use are for the oscillators, filter, and envelopes. The two oscillators have choices of Ideal, P1, P5, and the second oscillator has an additional setting called Bottom. The P1 and P5 are both a bit warmer sounding than “Ideal”, with P5 being louder than P1 when you use the Pulse and Saw together. The reason for this increase in amplitude is that the Pulse is inverted when using the P5 setting. The “Bottom” setting (only for the 2nd oscillator) has more of a defined triangle waveform.

The Filter settings are named Crispy, Rounded (both modeled from the hardware), and Driven (an u-he creation with a blend of settings). The two envelopes have the choices of Normal, High Sustain, One Shot, Piano 1, and Piano 2. The manual has the background on these, so I won’t go into details here, but I will say that they give you a good deal of variation to the envelopes.


The Sequencer has two 32-note patterns that will save with your preset. You are able to enter the notes one at time using the step-record function I mentioned earlier. The other way to add notes is to manually click on the cells values in each step, and drag the mouse up or down. A rest between notes can be added using the “Rest” button, and the cell  named “Type” lets you select between Tied, Rest, or a regular Note On setting. To enter the notes, you can click on the Repro-1 keyboard, or use MIDI keyboard. The patterns can also be saved and recalled for later use.

Repro-1 has five effects, and you can access them by clicking the “Effects” button on the far-left side of the keyboard. They include the Jaws Wavefolder, Lyrebird Delay, Drench Reverb, RESQ-Resonator/EQ, and the Sonic Conditioner (a type of transient/saturation effect). These can be individually switched on or off, or placed in whatever order you’d like using their buttons along the left side. They’ve also added a handy master on/off switch for all of the effects. All of the effects function well, and I especially like the Jaws Wavefolder. It’s a waveshaper that folds the waveform back on itself using a toothed curve, and there’s a control to adjust the amount of “teeth”. It can give the audio signal a type of distortion that sounds a bit like FM. One feature request I’d like to have for Repro-1 is the ability to modulate the effects.



Repro-1 is an extremely capable monophonic synthesizer plugin. I have never owned the original hardware, but it sounds like a great competitor to the Minimoog. It can be very smooth if it has to be, but can also cut through with more of a raw, edgy/gritty type of sound. I love the sound of the many presets included, and they really show off its important qualities. The manual is great, and the price is a bargain for how much has been included in this high-quality synth. As usual, u-he hits another home run. I guess that is just par for the course.

Repro-1 retails for $99 USD. You can get more info on Repro-1, hear audio demos, and download a demo version from the u-he website:





SoundBytes mailing list

Browse SB articles

Welcome to SoundBytes Magazine, a free online magazine devoted to the subject of computer sound and music production.


If you share these interests, you’ve come to the right place for gear reviews, developer interviews, tips and techniques and other music related articles. But first and foremost, SoundBytes is about “gear” in the form of music and audio processing software. .


We hope you'll enjoy reading what you find here and visit this site on a regular basis.

Hit Counter provided by technology news