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Kurzweil PC4

Performance Keyboard By Robin Bigwood
Published March 2020

Kurzweil PC4

Kurzweil's PC4 is a solid all-rounder with hidden depths...

Kurzweil are grandees of the big, complex, workstation-style keyboard world, with a history going back to the early '80s, and a remarkable legacy of products. The current Kurzweil pro-keyboard line-up encompasses stage pianos, workstations and, in the case of the PC4 on test here, 'Performance Controllers'. The name could be misleading: this is not just a MIDI controller (though it's capable of that), but a workstation-like synth in its own right. Whatever you want to call it, the PC4 sits in the middle of the Kurzweil range; more expensive and complex than the SP stage pianos, but cheaper than the Forte–series workstation and Artis stage piano. There is as yet a single 88-note version, but it wouldn't surprise me if a 76–note counterpart appeared at some stage.


Headline specifications are as follows. Two sound engines are on hand: VAST, which encompasses sophisticated sample playback, virtual analogue and FM layers, and Kurzweil's KB3 tonewheel organ emulation. Two gigabytes of factory sample content is supplied, leaving a further 2GB for user samples and other storage needs. Polyphony is 256 voices, with a fixed number of those non-dynamically allocated to the KB3 engine when it's in use. Sixteen multitimbral parts can be active at once, with the proviso that you're limited to a single KB3 organ instance. Over 1000 single-sound Programs and 50+ layer/split Multis are provided from the factory, with room to add 4096 user versions of each. An onboard sequencer with basic but useful editing facilities lets you layer up your 16 PC4 parts, and/or drive external MIDI gear. And, finally, the effects provision is extensive — 32 effects units in total, available to be deployed at master and part level, as two aux send/returns available to all parts, and even to the individual layers that make up a part.

The hardware side of the PC4 is an interesting mix too. The case is plastic (though seemingly tough), and this helps to achieve a very manageable 13kg overall weight. Keys are velocity- and aftertouch-sensitive, and the word on the nerdy piano forums is that it's a Medeli (rather than, say, Fatar) action. White-key dip is 10mm, with black key fronts sitting 12mm above — entirely unremarkable, neither particularly deep nor shallow. Nor is it either notably light or heavy, but somewhere in the middle, so a good choice for this type of keyboard, where you're playing acoustic piano one minute and monosynth sounds the next. The action is a little noisy, with some hollow-sounding bumps from the case on both key down and release. There's also almost no give at the bottom of the key travel, and you'll need firm fingers to explore aftertouch response. Overall, though, I have few criticisms of this keyboard. It's not as nice as a top-of-the-range Fatar, Kawai, Roland or Korg, there's no wood in it and no escapement feel, but it's a lot better than budget 88-note clunkers.

Real-time controls come in the form of a bank of nine sturdy sliders, knobs and buttons, pitch and mod wheels, and a Variation button. The rest of the user interface is based around a 480 x 272–pixel colour LCD with six soft buttons, and a whole panel's-worth of dedicated buttons for mode and sound selection, transposition, tempo and transport functions, and navigation. There's also a large 'alpha dial' that's essentially just a value wheel, in the style of an old-fashioned iPod.

Round the back we find MIDI and USB ports to the left and a generous selection of pedal inputs and audio I/O to the right.Round the back we find MIDI and USB ports to the left and a generous selection of pedal inputs and audio I/O to the right.

Connections to the outside world are good. Two quarter-inch output pairs can be configured as a mirror or as separate stereo outs, flexibly fed from internal parts. Not only that, but a quarter-inch input pair can be routed through onboard effects, and there's an 3.5mm stereo socket as well. For those that like to give their feet something to do, the PC4 sports two continuous pedal inputs, and two sockets for switch-type pedals which can handle no fewer than four switch pedals if they're wired appropriately. There's just a MIDI In and Out on five-pin DIN sockets, but USB A and B sockets allow for the use of thumb drives as well as a computer connection. Power enters via a 15V 2.5A mains adapter: rather disappointing given how grown-up the rest of the I/O provision is, and it doesn't help that there's no strain relief for the input plug, although the adapter itself looks to be of good quality and runs cool.

Shallow End

After an approximately 22-second boot-up time, the PC4 is ready to use, and with program names appearing on the LCD screen with informative pictorial backdrops (of piano keys, orchestral instruments, details of Prophet VSs and Minimoogs, etc) it's all very inviting.

A colour backdrop typical of Program mode sound selection, and one of the editing screens you can access with the front panel EDIT button.A colour backdrop typical of Program mode sound selection, and one of the editing screens you can access with the front panel EDIT button.Program selection can be done in multiple ways, such as scrolling via the alpha dial, pressing Category buttons to leapfrog to your preferred instrumental group, and direct recall via an embedded numeric keypad and a Program's ID number. There are also 'Quick Access' banks, which are a kind of setlist feature, whereby the user can gather together any 10 programs at a time and recall them with a single button press. It does not appear to be possible to step through these using a pedal though.

Whichever way you do it, sounds come online pretty much instantaneously. And, happily, notes held or which are sounding from a previous program are often unaffected by loading a new one. Kurzweil don't make any formal claims for this kind of seamless transition, but it seems pretty robust in practice. The only exception seems to be going between KB3 organ programs, or from a KB3 to a VAST program, then we do hear a glitch, or silence.

This is as good a time as any to mention all those front-panel real-time controls. The most direct correspondence between sound parameters and labelling is for KB3 organ sounds. For VAST Programs it's slightly less obvious, with some parameters that look like they're on the knobs actually mapped to the faders. Unexpectedly there's a three-band EQ lurking in there too.

Setting up an ad-hoc keyboard split or layer is done via LCD soft buttons always visible in Program mode. They'll both switch you into the PC4's Multi mode, and immediately display full-width keyboard diagrams, with keyranges, selected programs and mute/active status all tweakable via cursor button and the various methods of program recall. Real-time control allocations change now, and synth parameters are sacrificed for part level and pan. Via editing screens (more about those later...) this can be changed and saved (per Multi) just as you wish.

Kurzweil PC4Here's a thing we need to get out the way sooner rather than later, though. The PC4's Multis are of the least sophisticated and most problematic kind, which is to say that they only contain references to individual Programs, and don't store program data itself. If you have five multis, say, that all reference the same program, and you one day happen to tweak that program (or indeed mangle it out of all recognition), all five multis are affected. I suppose this distinctly 1980s way of doing things is at least simple to grasp. The only other silver lining is that the PC4 makes it hard for you to overwrite factory Programs, and tweaks you do make will be saved into one of the many thousands of user memory locations. So if you're careful this dependency-related problem need never occur.

Using the PC4 as a MIDI controller is, thank goodness, much less contentious. Multi mode's keyrange displays really come into their own here, and setting DIN or USB output and channel assignments is easy. You can also independently transpose keyranges, adjust velocity curves and range limits, decide if zones transmit pedal messages (and so on), and opt to send out program changes when the Multi loads. Especially if you're using other hardware MIDI sources the PC4 makes for a really good MIDI controller: perhaps as good as anything out there currently.

Like all other Kurzweils I've played, the PC4 always felt willing, and musical, and is an extremely useful thing to have around for many live and studio applications.

Automatic For The PC

In contrast to that entire bank of real-time hardware controls, the PC4's arpeggiator gets a mere two buttons, one to turn it on and off, and one to latch incoming notes. That's because all other settings are made in an editing screen accessed via the EDIT button and a soft button beneath the screen. Then it turns out that the arpeggiator is amazingly capable.

It's a  long way from a  DAW MIDI editor, but the PC4's piano-roll display is at least informative. In the absence of mouse or touchscreen all event editing goes on in the attendant list.It's a long way from a DAW MIDI editor, but the PC4's piano-roll display is at least informative. In the absence of mouse or touchscreen all event editing goes on in the attendant list.Old favourites like 'up/down' are there if you know where to look, but they're amongst hundreds of far more sophisticated algorithmic, pattern-based and indeed programmable step-sequenced options, with independent velocity and duration patterns and other nuances. You might be glad of the 150 or so factory arpeggiator presets, and the ability to save your own.

This leads us nicely to Song mode, which relates to the onboard 16-channel MIDI sequencer. There are six hardware transport buttons, but again most work goes on in several different editing screens that are available after hitting the Song button. There's even a 'piano roll' display of sorts, which runs vertically and helps identify events that you'll still edit numerically, and mixer pages with simple graphical representations of track level and pan.

Although much less sophisticated than a computer DAW, this is still a useful sequencer, with quantising, an ability to handle controller and other non-note MIDI events, and surprisingly full editing features. It'll knock out complete songs and also lets you record smaller snippets that can subsequently be used as a so-called Riff: looped mini-sequences of drum beats or auto-accompaniment-type figures, triggered by pressing one note in a single zone of a Multi.

There's a limitation in terms of total memory (~50,000 events per song), and no means to vary tempo or time signature within a song. Also, the sequencing model is strictly linear, with no option to build up larger structures from smaller sequenced blocks, say, other than via copy and paste. Users must also be aware there's absolutely no undo function for editing actions.


Over decades past it's largely been the quality of Kurzweil's sounds that have made their keyboards so desirable. Generalising to a simplistic degree, they've sometimes sounded full and rounded when Japanese counterparts tended towards the memory-starved. Which is surprising, as Kurzweils often had less ROM memory than their competitors.

In-depth synthesis on the PC4 takes place through dozens of screens like these. These show one of the 'wiring algorithms' that define basic signal flow, parameters for LFO/envelope/function editing and one of the unusual multi-stage envelopes. The potential is immense, but it's all done with cursor and value dial, one parameter at a  time.In-depth synthesis on the PC4 takes place through dozens of screens like these. These show one of the 'wiring algorithms' that define basic signal flow, parameters for LFO/envelope/function editing and one of the unusual multi-stage envelopes. The potential is immense, but it's all done with cursor and value dial, one parameter at a time.While this generalisation isn't valid any more, the Kurzweil reputation for quality is still very much intact and lives on in the PC4.

Every stage piano or workstation needs a 'flagship' piano, and here it's the German D '9ft' Grand. Initial impressions: really full and healthy-sounding, classy, dynamic, responsive, playable. Half-pedalling (with a compatible sustain pedal) and sympathetic resonance features help with the realism aspect. Several companion programs offer variations of the same sample set (bass starved, muted, velocity-skewed versions, etc) and you'll often be able to zone into the style of piano you like through preset selection alone.

Although it's not always obvious if other piano programs are varying sample sets or just keymap or algorithmic processing settings, there do seem to be several other source pianos on offer, including a 7ft studio-style grand, and one based on far less naturalistic but still useful 'legacy' samples from Kurzweil K2600 days. The variety is immense, and in many typical performance contexts — rock bands, worship, theatre work — you'll feel spoilt for choice.

If you are looking for absolute cutting edge, state-of-the-art piano replay though, this is not it. The sampling is neither as deep nor three-dimensional-sounding as you'll hear from a Nord, and there isn't the fundamental flexibility that comes from a system with a modelling component, like Roland's SuperNatural. Factory presets don't seem to offer piano-wide sustain pedal resonance (which is different, and potentially more telling than note-based sympathetic resonance), or una corda samples. Upright pianos are clearly not made from true upright sample sets, but are just kludged and detuned grands.

Kurzweil PC4Worse, though, I discovered that in the firmware I tested, v1.06, many piano programs have out-of-tune notes. The flagship Program 1, for example, has four frequently used bass notes that beat obviously with octaves and fifths played above. The discrepancy moves to different pitches when the sample keymap has been modified for other programs, but it's not only the 9ft sample set that seems to be affected. In fact, only the old legacy piano sounds were bang in tune. I asked Kurzweil about it, and they said they're aware of the issue, are investigating, and plan to fix it in an update. It's not a difficult fix — a user prepared to investigate it and work through all the affected velocity layers could in fact fix it themselves — so I'm sure this will happen.

Keyboard sound provision goes on, as you'd expect, via dozens of Rhodes, Wurlitzers, Clavinets and harpsichords. Everything is very playable, and all sounds reassuringly hi-fi. Like the pianos, they don't survive forensic examination of velocity sample-switching, but again, with my pragmatic hat on, most will sound very good in a live setting or within a mix.

The KB3 tonewheel organs do stand up to close scrutiny. They're immensely vibey, they can sound soulfully knackered one minute, and potently clean or driven the next, and to my ears the complexity of the Leslie rotating speaker effect on offer here (with rotation speed toggled by the front panel Variation button) is pretty magical. Pipe organ sounds are also of excellent quality and are offered as single stops which combine beautifully into layered registrations. An entirely different matter to many lesser keyboards' single, hideous, garish 'Cathedral Organ' sound.

Kurzweil PC4Amongst the virtual analogue synth sounds there's quite a bit of name-checking from synth history, with various characterful Moog, Oberheim and Roland-inspired sounds. Good basses, pads and leads alike, as well as lots of multi-layer D50-esque timbres. Real-time controls get you so far with shaping these further, but a true knobby interface is sorely missed, and of course the hammer action keyboard feels all wrong. I was surprised I didn't hear the PC4's parameter-automatic CC Sequencers more often amongst synth presets, but this parameter automation/animation feature is there when you want it.

Through the many hundreds of string, wind and brass programs, the quality stays very high. There are solos, small ensembles and sections, and some are nicely 'contemporary' in nature, and very playable. The Variation button often switches in octave stacks, or (for strings programs) pizzicato alternatives. There is not, though, any other ready-done provision for accessing multiple articulations in real-time, as we've grown used to with software samplers, and no evidence of a 'scripted'-type playback for hyper-real representation of solo instruments.

With the same proviso (of there only being single articulations on hand) guitar and bass sounds are about as good as you're likely to get at this price. The dozens of drum kits cover most styles imaginable, with a really good provision of tuned percussion to back them up.

Who's The PC4?

Summing up the PC4 is surprisingly easy. In most performance and studio situations it feels just like a good stage piano: preset-based, immediate, reassuringly simple, and with a handy sequencer at the ready. If you like the Kurzweil sound, the more than respectable keybed and overall balance of features, this might be all you need to know. However, go down the EDIT button rabbit-hole and everything changes: if you can learn its ways you'll have a powerful, complex sampler/synth and organ emulator at your disposal.

Quality of preset sounds might be the thing to consider most carefully. The acoustic pianos, as I mentioned, are not quite as good as on some other keyboards costing about the same as the PC4. But where they lack soundset breadth and editing depth, the PC4 offers it in spades. And by most standards, and thinking about real-world use, it sounds excellent (we just need that crucial firmware refinement to make the pianos as good as they can be).

Like all other Kurzweils I've played the PC4 always felt willing, and musical, and is an extremely useful thing to have around for many live and studio applications. If you're looking for an all-rounder get it firmly on your shortlist: it could be everything you need.


At a street price of £1800$2000, the PC4 is undercut by Yamaha's MODX8: that's a workstation of sorts too with somewhat friendlier synthesis features, but its sequencer is crude and there's no dedicated organ emulator. A fairer comparison might be with Roland's highly regarded RD-2000, which has a top-flight key action, excellent acoustic and electric pianos, and at least as good organs, though no sequencer at all and nothing like the programming depth. A Korg Grandstage 88 offers a far simpler and more direct user experience, and a Nord Piano 4 even more so, but its piano sounds are arguably unsurpassed.

Deeper & Down

If you have experience of the way most modern–day keyboards pan out, you'll have noticed that everything I've described about the PC4 so far is closer to the vibe of a stage piano than a workstation. So what of this 'Performance Controller' business?

Well, lurking just beneath the user-friendly surface, and mostly accessed via the innocuous front-panel Edit button, is a whole universe of possibilities that most stage pianos could only dream of, even in their most reverb-soaked out-there moments. It's a full, unlimited synth and effects architecture in which every single parameter of the PC4's sound engines can be accessed.

Starting with the VAST architecture, let me tell you that name is appropriately descriptive... This is a sound engine of prodigious complexity and potency. A single program can have up to 32 functional 'layers', each with oscillators, sample keymaps, filters and signal processors flexibly deployed according to hundreds of provided algorithms, some with signal splitters, combiners and feedback loops. There are no less than 22 different types of virtual analogue oscillators, plus FM oscillators with their own DX7-derived algorithms, and multi-waveform possibilities. Arcane delights such as FUN[ction] blocks perform maths and logic functions on incoming signals, and there are remarkable AAAD(S)RRR loopable envelope generators (no, the cat didn't just walk over my computer keyboard).

Just one VAST layer can sound really good, supported by a plethora of very good-quality effects (which can be inserted in ready-made chains). A bunch of layers together will support the most ambitious and outlandish sound design or sample replay requirements.

The flip side is that working with VAST frequently recalls the worst of 1980s digital synth practice, with programming interactions all done with cursors, value dials, numerical values, and nary a knob in sight. The clear colour LCD does at least show visual representations of algorithms, envelopes and (in a basic way) keymaps, and on some pages presents multiple numerical parameter values at a time. But for anyone who enjoys free-rolling, aimless synthesis explorations, via knobby analogue interfaces, VAST's dozens of parallel and nested editing screens might feel like torture.

There's also the matter of polyphony. The headline 256 voices on offer is good, of course. But every VAST layer uses a voice. So if you do go all-out and program a 32-layer program, that leaves your PC4 capable of playing just eight notes.

The full 'Musician's Guide' PDF manual does at least explain VAST thoroughly (even if it does take on a little of the character of a nuclear power station textbook at times). Terminology like 'User Object', 'ID', and algorithm makes a lot of sense when you have history with Kurzweil products, but isn't self-explanatory for newcomers.

The PC4's other main sound engine, the tonewheel organ-emulating KB3, is far easier to grasp. You can only enable one KB3 instance, at which point it grabs somewhere around 45 voices of the overall 256–voice polyphony count. Then it (intriguingly) uses DSP-generated waveforms for the lower half of the tonewheels, and samples for the upper. The possibility of using organ keymaps with sawtooth waves rather than sines, and thereby explore transistor organ territory, is really welcome.

Compared to a Nord tonewheel model, say, the PC4 is much more tweakable. Via editing screens you can vary the total number of tonewheels in use, to accurately match the varying design of Hammonds from across the decades. Or use organ keymaps that vary amplitude between individual keys or tonewheels, to change character or deliberately introduce imperfections. Tonewheels can also be tuned, or made to virtually 'leak', electrically speaking, into each other. Adventurous programmers can further use VAST algorithm processing blocks — LFOs, envelopes, function generators, etc — with KB3 timbres.

The Outside World

When you need something beyond the factory programs, the PC4 can import all kinds of data from an inserted USB drive to its 2GB of Flash memory, which is fast-recall long-term storage that survives power cycles.

At the time of writing this review, Kurzweil hadn't provided any additional soundware in the PC4's native format, but it handled various PC3 and Forte-series programs and sample-based sounds I threw at it. There's some valuable stuff out there to be ingested: lots of PC3 banks, plus SP6 and Artis sounds, and DX7 patches in SysEx. With a little effort and experience you can create your own unique sounds from imported 8- and 16-bit WAVs and AIFs. A Soundtower-based Windows and Mac OS software editor, which might help with this and many other tasks, was not available during the review period but may well be by the time you read this.


  • Broad, high-quality soundset with some fine acoustic piano sounds.
  • Stage-piano ease of use, underpinned by accessible, massively capable synthesis features.
  • Sixteen-part multitimbral, with multitimbral effects.
  • Generous provision of real-time controls, pedal connections, and audio I/O.
  • Good hammer-action keybed with aftertouch.


  • A disconnect between surface-level simplicity and potentially bewildering, laborious programming depth.
  • Old-fashioned referenced Multis, despite huge user memory provision.
  • External power adapter.


The PC4 is a really useful, portable mid-range all-rounder. Some aspects of architecture and programming betray their decades-old roots, but the package as a whole feels well rounded.

Published March 2020