Kilohearts Phase Plant 2.1 – the Synth and Software Review

It does virtual analog, granular synthesis, wavetable synthesis, sample playback, and FM.

We’re truly living in a Golden Age of synthesis. Every year more developers step up with amazing new synthesizers. Both the software tools for building instruments and the slick ideas for how an instrument ought to work are more advanced than ever before.

Kilohearts is not as high-profile a company as some of the big guns, but it would be a mistake to breeze past their Phase Plant synth. This thing is a true monster. It does virtual analog, granular synthesis, wavetable synthesis, sample playback, and FM. For most practical purposes, it’s a modular design, though the user interface doesn’t look very modular. And it’s just plain packed with features.

At $199, Phase Plant is not cheap, but that’s not the end of the story. It’s part of a larger ecosystem – a set of Kilohearts products.

They have a large suite of free effects plugins, which are included within Phase Plant and can also be used as separate plug-in effects in your DAW. Extra banks of Phase Plant presets by third-party developers are typically $29 – but wait, there’s more.

For a subscription price of $9.99 per month you get everything, not only Phase Plant, a couple of platforms for combining their effects, and half a dozen non-free effects, but also all of the third-party patch banks, including those that may be released later. I’m not a fan of subscription-based software, but I feel this deal is almost too good to pass up.

Figure 1. The main user interface of Kilohearts Phase Plant. Along the top are eight macro knobs, which can be defined differently for each preset. The small orange circles next to the knobs indicate modulation routings. The left-side panel contains generators (mainly oscillators with their associated amplitude envelopes). At the upper right are three lanes for audio processing. The rack of modulation sources is along the bottom. The strip above the modulation sources contains the global controls.

Overview. The main user interface of Phase Plant is divided into three separate areas: one for oscillators and related items, which Phase Plant calls generators, one for modulation sources, and one for audio processing (see Figure 1 abovee). In addition, there’s naturally a patch browser. Pop-up windows for detailed editing can be called up by clicking on little pencil icons. Within each area, modules can be added as needed; there’s not a fixed limit to the number of modules of each type.

The user interface is consistent throughout the panel. Individual modules and groups can be turned off to audition the sound without them. If you have a lot of modulators or a lot of processors, you can minimize their footprint in the panel using a very standard computer-type click. Dragging modules around is just as easy.

It’s a sensible design, but one or two details tripped me up at first. As the manual explains, the modulation sources run at a slower clock rate than the audio sampling rate. And the filters are normally in the upper right quadrant, along with the effects. So if you need audio-rate modulation of a filter, what do you do?

It turns out you can also insert a filter into the generators area, in which case its modulation input can run at audio rate. Having done this, you can modulate its cutoff from a different generator. This is also how you do FM sounds: one oscillator can modulate the pitch or phase of another oscillator.

Figure 2. The patch browser in Phase Plant is organized into folders, and each patch has a favorite button, a short text description, and the name of the author.

Presets. Kilohearts has called on a number of sound designers to provide presets for Phase Plant. The browser (see Figure 2) houses a number of folders. If you find a preset that’s almost what you need but not quite right, you can nudge it with the macro knobs, which are displayed below the preset list, in order to find out quickly if the preset can be made to work.

I was impressed with the presets, most of which are very usable. Many are downright inspiring. And there are a lot of them! (No, I didn’t do a count.) The categories include not just the expected bass, lead, keys, pads, and mallets, but chords, sequences, drums, FX, risers, and several types of basses. There’s even a folder of tutorial patches with more than 30 items, to make it easier for you to see how to do your own FM, layers, a key-tracked filter, and so on.

Every patch has a bit of explanatory text in the list. When you find something you like, you can click on a Favorites button. All of your favorites can be displayed in a separate list. There’s also a handy Search function in the browser, so you can search for presets that are gritty, warm, distorted, or whatever.

Generators. The five generator types are analog, granular, noise, sample, and wavetable. Each generator includes both an oscillator and its own amplitude envelope (an ADSR with added delay and hold stages). Having an integral envelope is handy, as it encourages sound designers to layer sounds with different amplitude envelope shapes. The curvature of the attack, decay, and release segments is editable graphically.

All of the generators (other than white noise) include not only a tuning parameter in semitones and cents but also harmonic, linear frequency shift, and phase parameters. The harmonic setting is very useful if you’re setting up an FM patch, because the modulating oscillator can be reliably tuned to an upper or lower partial. The shift parameter changes the way the oscillator tracks the keyboard, which can be useful for oddball nonlinear tunings. It also furnishes a way to use one oscillator to add vibrato to another, though normally you’d do this with an LFO.

The analog oscillator is simple: sawtooth, square, triangle, and sine waves, exactly as you’d expect. These waveforms are anti-aliased, so the upper octaves don’t fold over, but the sawtooth is a bit jittery in the octave below Middle C (MIDI note 60). I found that it could be smoothed out somewhat using a lowpass filter within the generator, but this is one of those edge cases where virtual analog doesn’t actually sound analog.

The square wave has a pulse width knob. A sync knob and a unison button are available for all of the waveforms. The implementation of unison doubling is powerful; in addition to the expected detune, stereo spread, and blend knobs there’s a menu for choosing chord types. I used the Shepard tone setting in this menu to create a humorous lead; the Shepard setting causes all octaves to behave the same way, so you can play up or down a four-octave scale without ever leaving home base.

The granular Generator offers a fairly standard set of parameters. One nice difference is that instead of a menu for selecting the grain envelope, the attack and release times of the grain envelope are freely editable, and can be modulated, for instance from velocity. A standard unison mode wouldn’t make much sense for granular synthesis, but the chord presets are available.

Phase Plant ships with a good set of samples, which can be accessed from a browser window that pops up in either the granular or the sampler Generator. Instead, you can drag and drop samples from your hard drive onto either the granular or the sampler.

The sample player Generator is, again, about what you’d expect, with sample start time and loop length parameters, back-and-forth looping, and so on. One of the limitations of Phase Plant is that it isn’t set up to do multisample keyboard layouts. You can do a bit of key zoning by routing MIDI note number through a Remap modulator and using it to set the output level of one sample or another to zero or full-on depending on what key you play (as illustrated in Figure 3), but all of the samples will still be responding silently to every note you play, so the CPU load will start to add up.

Figure 3. Want to set up key zones for different Generators, so as to create a split keyboard or a drum kit? Send the MIDI note number (a modulation source) through the Remap Editor (a modulation signal processor) to the amplitude of an oscillator, and then edit the input-to-output mapping as shown in this graphic window. The Remap Editor is good for lots of more complex remappings as well.

The wavetable oscillator has a familiar 3D graphic display of the kind seen in other high-end synthesizers. More than a hundred different tables are available from a menu, and you can edit the individual frames within a table if you dare. This is not an exercise for the faint of heart, but it’s possible.

The noise generator has three types of noise. Its white noise source is just pure white, so adjusting its frequency would make no sense, but the smooth and roughly stepped noise types can be frequency-modulated. All of them can be used as FM sources. There’s also a stable/random switch. If you choose stable, the noise will be the same on every keystroke. This is a subtle distinction, but sometimes it’s useful.

The generators area also includes a curve generator. This is a bit like a multisegment envelope, in that you can select a complex curve that will loop, and then adjust its loop start and end points. It can be used for modulating other parameters within the generator area. It’s not a true multisegment envelope, because if you lift your finger from the MIDI key while it’s somewhere in its loop, it won’t jump immediately to the release portion.

Figure 4. This pop-up menu lists all of the available audio processors. Those that are not authorized in my account are grayed out, and can’t be selected.

Processors. There’s nothing truly remarkable about Phase Plant’s list of audio processors (see Figure 4), but it’s a good solid list. What’s cool is that if you load a preset (such as some of those in the third-party content) that uses one of the non-installed Kilohearts effects, the preset will still work perfectly; you just can’t edit that module.

The output of each generator can be routed to any of three lanes in the processing area on the right side of the panel. These lanes can contain both filters and effects. Normally the output of lane 1 is routed to lane 2, lane 2 goes to lane 3, and lane 3 goes to the output, but you can easily change this if you want to, for instance by putting the three lanes in parallel rather than series. A three-oscillator sound in which each oscillator has its own filter and effects is easy to set up.

Each lane has a Poly switch. If this is not activated, the lane will process together all of the signal that arrives at it. This is fine for most effects processing, but a filter should normally be separate for each voice. Hit the Poly switch for a lane and the filter(s) in that lane will be polyphonic, as will everything else in the lane.

The standard filter is multimode, but there’s also a lowpass ladder filter with a saturate button that turns on the drive and bias knobs. There are fewer multimode options in the nonlinear filter, but more types of saturation. The resonator can be tuned to any pitch, and can track the keyboard fully or fractionally using the Note module in the modulators area. There’s also a formant filter with X/Y modulation of the formants. The strength and number of the peaks in the comb filter is not adjustable, but it’s an okay comb.

Just for fun, I set up my sustain pedal to cue the tape stop effect. It worked fine.

Figure 5. When an ordinary LFO won’t do the job, try a wavetable LFO. Phase Plant has dozens of wavetables, which can be used either by audio oscillators or by this type of LFO. The wavetable choices are available in this menu. Can’t find quite what you want? Open up the wavetable editor and edit one frame of the table at a time using tools with names like Disperse and Tilt EQ.

Modulators. In the Modulator section along the lower part of the panel, you can create and edit any number of LFOs, envelopes, and other widgets depending on your needs, limited only by the CPU power of your computer. These envelopes are DAHDSRs, as in the generator section, with freely editable (and modulatable) curves for the attack, decay, and release segments. The LFOs have editable contours, and can be used quite easily as step sequencers. Wavetable LFOs (see Figure 5) add some new possibilities for sound design.

As noted above in the section on generators, Phase Plant lacks multisegment envelopes. You can set an LFO to one-shot mode and then give it a complex multi-contour curve that you’ve edited yourself, but once it hits the final point in its travel, it will just stay there. There won’t be a separate release segment or segments.

I wouldn’t mind seeing a more robust implementation of step sequencing. You can set up an LFO to cycle through a series of up to 128 pitch steps, but there’s no direct way to retrigger any of the envelopes from the steps. Instead, you would set up a different LFO with an attack and decay so that it loops once for every 16th-note or 8th-note, and then use that to modulate filter cutoff or oscillator amplitude.

The trance gate effect, which can operate polyphonically, is also useful in creating rhythmic stepped patterns. This trance gate stores up to eight patterns, but for some bizarre reason the pattern selector can’t be modulated, and it can’t be automated either. I’m told this omission may be remedied in an update.

To use a modulation source, you click the orange plus sign in its lower right corner, as shown in the video. At this point, all of the destinations that are available for it will also acquire plus signs below them. Click on one of those and drag up or down, and you’ve added a modulation routing. The strength of the modulation will depend on how far you dragged. If you need precise control, right-click and edit the modulation amount in a text box.

This open-ended modulation routing is what qualifies Phase Plant as a modular synth. The standard idea of a modulation matrix, which is found on many software synthesizers, is starting to feel rather old-fashioned and limiting.

If you want to change the LFO depth from the mod wheel, the way to do it is to add a MIDI CC module, wiggle the mod wheel to tell that module what Control Change message type you want to use, and then route the output of the MIDI CC module to the amplitude slider of the LFO. This is easy to do, but it’s a bit less intuitive than the method used in a mod matrix list.

The remap module can be used to turn any modulation signal into something more interesting, perhaps by adding multiple levels or by changing the velocity response curve.

Final verdict. Phase Plant is a powerhouse. It has a ton of inspiring factory presets, several types of great-sounding tone generators, a variety of filters and effects, and very flexible signal routing. While learning to use it I found myself making and saving new patches, and that’s not something that always happens.

Yes, there are a couple of limitations: multisegment envelopes and multisample layouts are implemented only in a primitive form. But every instrument has limitations.On the whole, Phase Plant is a worthy competitor to other high-end synths. There’s no 30-day demo download, but it’s easy enough to sign up for the subscription, try it for a month for ten bucks, and then cancel the subscription if you’re not blown away. I’ll bet ten bucks you will be.