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Kurzweil K250 (Retrozone)

Workstation Keyboard
Published February 1999
By Philip Meehan

Philip Meehan fondly remembers his first love — a keyboard with the voice of an angel, the mind of a genius, and the body of a heavyweight boxer in a big black coat.

'Oh my God! Did you know it was that big when you ordered it?' If I had a pound for every time I heard someone shout that immortal line upon first seeing my gorgeous Kurzweil K250, I would have enough money to buy another one.

Kurzweil K250 workstation keyboard with Apple Macintosh.Mind you, it was big. Very big. With a fully weighted 88‑note keyboard, separate 'pod' power supply and attached Apple Macintosh computer, the Kurzweil K250 nestled in the corner of my flat with all the delicacy and grace of a gorilla in the back of a Reliant Robin. No wonder there was no mention of 'weight: 95lbs' on the specifications page. Even so, however, it was still a lot more compact than a nine-foot Steinway Concert Grand — and that was the point.

New Kid On The Block

The Kurzweil Music Systems K250 keyboard first appeared in 1984, the progeny of acclaimed software guru (and associate of Bob Moog) Ray Kurzweil. At that time, the top end of the music-technology scene was dominated by computer-based systems such as the Fairlight CMI and the NED Synclavier, both of which cost an arm, leg, head and torso and required a lot of typing to operate. The £12,000 K250 took a somewhat different approach: though similar in some respects to its computer-based rivals, it was first and foremost a musical instrument. Unlike most computer music systems, you could simply turn the K250 on, sit down and start playing — it instantly defaulted to preset 1, the glorious 'Kurzweil Grand Piano'. Even today, 14 years later, that sound is still hard to beat for accuracy, delicacy and sheer playability.

The most impressive aspect of the K250, however, is just how far it was ahead of its time. Take a look at these specifications: 88-note velocity-sensitive wooden keyboard, 341 standard presets from 96 ROM-based instruments, 18-bit floating-point resolution, user-sampling function with rates up to 50kHz and full sample editing, up to six layers and 31 samples per setup, up to 87-way keyboard splits(!), fully assignable filters and envelopes, 24 LFOs, chorus/flanging/delay, 12,000-note multitrack sequencer with punch-in/out, mute/solo/fader automation, event editing, MIDI and tape sync, Apple Macintosh computer interface for saving/loading of samples and setups, comprehensive MIDI spec and separate outputs on both jack and balanced XLRs. Even by today's standards this is fairly impressive — but remember, if the keyboard player from Hanson had bought a K250 when it first came out, he would have been two years old.

Black Beauty

The Kurzweil 250 originally appeared in two versions, the K250, with its beautiful 88-note wooden keyboard, and the 250XP Expander, which looked similar, but had the keyboard surgically removed (although the red felt dust strip along the front edge of the casing still remained!) Several years later, the 250XP was repackaged as the 250RMX Rack Mount Expander, shoehorning the contents into a 19-inch rackmounting 'cube'. The K250 and 250XP both featured the 'mean and moody' sculpted black body that Kurzweil used to great effect in the pre-launch publicity photos for the instrument, gaining a reputation at shows as 'something to look out for'. The front panel featured four master sliders (for tuning, panning and volume), three assignable sliders, 43 function buttons (all with LEDs) and a central 12-digit keypad with two-line LCD display. This central keypad could also be used to access three 'bins' of 10 pre-assigned presets, allowing the user to switch instantly between presets whilst playing.

Unlike anything else I had played at the time, changing between presets on the K250 did not cut off any currently-playing sounds. Instead, existing notes continued to decay (or sustain) with the 'old' sound, while any subsequent notes played used the 'new' preset. With judicious use of the sustain pedal and assignable sliders, this made the K250 a real performance instrument — you could sustain a string pad, then call up a piano and play over the top of it, switching between sounds without ever 'clipping' the end of a decay, or changing a voice mid-stream. Although all 250s were only 12-voice polyphonic, they utilised a hugely complex 'channel-stealing' algorithm that actually looked at what notes you were playing and removed the 'least musically noticeable' first, giving the impression that there were a lot more than 12 voices in operation, even with long decays and heavy sustain.

The sustain pedal itself is worthy of note: a wobbly plastic footpedal on the end of a jack lead was simply not good enough for Kurzweil! Instead, the 250 series had a 'Pedal Pod' — a large black box which contained the external power supply and two metal piano-type pedals. This connected to the keyboard's rear panel via a thick, python-like cable and a huge multicore connector of the type normally used to link together supercomputers or nuclear weapons. Once situated under the table, however, the Pedal Pod's sheer weight made sure that the footpedals never drifted far from where you left them...

The K250’s built-in sequencer contrived to be both sophisticated and intuitive. The K250’s built-in sequencer contrived to be both sophisticated and intuitive. This kind of design innovation is what I love most about Kurzweil products, and most of all, the K250. It felt like it had been designed by frustrated musicians, rather than assembled by an American electronics company. Even the seemingly endless 413-page manual had an easygoing feel to it, with sections written "by Bill Gardner" or "Chet J Graham" — people who probably owned K250s themselves, rather than just being employees in a technical writing department. The K250 fulfilled a great number of electronic instrument wish list features, with envelopes and delay parameters being calibrated in seconds and milliseconds (rather than the usual arbitrary 0 to 100), and a sequencer that had two big buttons marked PLAY and RECORD which worked as soon as you hit them, rather than after scrolling through several setup pages (in the process forgetting the million-selling riff you'd just come up with).

That said, the K250's sequencer was far from primitive. If you wanted to just play something over a loop and add a couple of parts on top, you could do that from the front panel without ever stopping playing — all the necessary buttons were there and were 'live' rather than menu-driven as on most modern keyboards. If you wanted to use the sequencer more creatively, it had full event and track editing, quantisation (with undo!), cut and paste editing, song chaining and even automated mixdown using the front-panel sliders and buttons. Although built-in sequencers on keyboards have, not unfairly, been seen more as gimmicks rather than true compositional aids, the K250's sequencer could actually be used in real life rather than as a glorified arpeggiator.

OK Computer

Even the very first K250s came with a built-in computer interface as standard. Though not SCSI (that was to come later) it allowed the keyboard to be linked up to Apple Macintosh computers. A program called MacAttach could be used to save and load samples, setups and sequences. Kurzweil released several volumes of additional sounds on floppies that could be loaded in via the Mac — much of the same library is still available for the K2000/K2500 today.

MacAttach was superseded by QLS, the Kurzweil Quick Load System, and later versions of the K250 could use a QLS function called 'SD Convert' to interface with Digidesign's Sound Designer and Softsynth programs to form a very powerful computer music system. And, believe me, back in the '80s you were nobody if your music rig didn't have a glowing VDU and QWERTY keyboard attached to it...

Not Just A Pretty Face

Although its main selling point was undoubtedly its marvellous Grand Piano preset -- and its 'Steinway meets Star Trek' looks — there was much, much more to the K250. Just as with the more recent K2000 and K2500, the inbuilt sounds were simply the starting point for a respectable amount of signal processing that could be used to tailor the sound with great subtlety. 'Timbre Shift' used a combination of detuning and pitch-shift to alter the basic tone of a sound from dark to bright in a way no filter ever could — shift the grand piano down by nine semitones and it sounded exactly like a soft-pedal version, while shifting the strings down by 29 semitones gave you a menacing orchestral backing sound that Trent Reznor would kill for.

Kurzweil's filters have always impressed me — although digital, they can close all the way down to silence, much like the analogue filters on ARP and Moog synthesizers. The bass end of the K250 had to be heard to be believed — putting one next to a DX7 was like comparing a Harley Davidson with a Magimix. Also, the dynamic range of the K250 was a terrifying 105dB, allowing sharp, percussive sounds like vibes and marimba to be played with alarming realism. In fact, many of the basic sounds on the K250 are still strikingly realistic even by today's 24-bit, 96kHz, phase-accurate stereo standards.

This was due to two things: partly, an advanced sampling process that Kurzweil devised called 'Contoured Sound Modelling', and mostly, a really good ear for great-sounding instruments. I still find myself ploughing through endless sample CD-ROMs containing beautiful recordings of awful-sounding instruments. As the K250 showed, however, the secret is to get the instruments themselves to sound good, and be played by musicians, rather than simply to rely on good microphones and 24-bit recording.

In my opinion, a bad recording of a good performance will always outshine a good recording of a bad performance — that's why James Brown, Lalo Schifrin and Isaac Hayes get sampled a lot and Mike Stock, Matt Aitken and Pete Waterman don't. Kurzweil's combination of beautiful recordings and mainframe computer-based processing blessed the K250 with a ROM sample set unlike anything produced before, or maybe even since. Sure, you can buy a CD-ROM with a 128Mb Steinway sample set on it, and load it into an Akai or an Emu, but, when compared with the K250's humble 512k Kurzweil Grand Piano it just doesn't sound as nice... The K250's sounds are such that people listen to them and say 'that sounds good' rather than 'hey, that's a startlingly realistic-sounding piano sample'. The same goes for the legendary 'Cathedral Choir' preset, as well as others like 'soft tenor sax' and the solo cellos.

The K250's ensemble string samples were the same as those used on Kurzweil instruments today, simply because they haven't been bettered. OK, they were mono, but layer them, map them to the left and right outputs, add a touch of built-in chorus and you have the soundtrack to Die Hard at your fingertips. In much the same way as the Fairlight CMI or Synclavier, the Kurzweil K250 had a select following of fans who based their particular 'sound' around it. Film composers such as Michael Kamen used it excessively to create massive orchestral soundtracks — something at which Kurzweil keyboards still excel — and classic '80s albums such as Talk Talk's Colour Of Spring or Filigree & Shadow by This Mortal Coil used the K250 to such great effect as to almost become demo discs. In much the same way as the Mellotron or Hammond B3, the K250 was an instrument with character — I defy anyone to spot a Roland or Yamaha synth preset in a mix, whereas the K250 simply oozes class, adding an imperceptible something to every track it's used on. In fact, I imagine the reason that nobody has bought out a CD-ROM of K250 samples is simply that Kurzweil are still to this day proudly possessive of their sounds.

Evolution, Not Revolution

So what happened to the mighty K250? Well, unlike many of its rivals it managed to do something quite extraordinary — it evolved. Whereas the Fairlight CMI and Synclavier both disappeared, their thunder well and truly stolen by high‑street samplers like the Akai S900 and home computer sequencing software, Kurzweil repackaged the K250's sound ROM into a range of low-cost modules, the 1000 series. 1987 saw the release of the K1000 keyboard (and 1000PX Expander module) which featured a close, but not identical copy of the K250's Grand Piano, with ensemble strings, choir and other sounds in a playback-only form for around £1200.

The remainder of the K250 sample set was loaded into a range of 2U rackmount boxes called the 1000SX String Expander, the 1000GX Guitar Expander and — wait for it — the 1000HX Horn Expander (stop sniggering at the back...). The beautiful 88-note piano keyboard turned up on a range of controller keyboards and 'home piano'-style instruments, while the user-sampling facility took a well-deserved break, disappearing for a while from the Kurzweil product range. This repackaging of company 'assets' using low-cost technology was a bold move for Kurzweil, and whilst undoubtedly successful, the company didn't really hit the big time again until the release of the K2000 in 1992. This and the subsequent K2500 have put Kurzweil back on the map, being arguably the best workstations of their type in the world. My own K2500 features 128Mb RAM, full digital in/out, a weighted keyboard and a dinky little chain of SCSI devices, but somehow... when I want that piano sound, I still turn to the gorilla in the corner. The K250 may be big, but it sure is beautiful.

A Career In Modelling

The K250's user-sampling section, or the Sound Modelling Program as it was called, was extremely powerful in its time, but looks a little primitive today. At the 50kHz sample rate, a standard K250 had only 10 seconds of mono sample time, but this could be expanded with the SUPERAM 1 and 2 boards, which boosted it to 20 seconds and 40 seconds respectively (and, as a consequence, filled the K250 with more chips than Waynetta Slob).

The sampling process was a variant of Kurzweil's mainframe-based 'Contoured Sound Modelling' used to create the 18-bit ROM sounds and, to my ears, sounded like 12-bit sampling, with a tell-tale quantisation 'fizz' at the end of decays. To improve matters, there were six sample 'modes' optimised to the type of sound you were sampling — sustained sounds, slow-decay sounds, normal-decay sounds, fast-decay sounds and speech. A sixth mode, called 'quick take', allowed you to 'roughly' sample a sound and play it back immediately — which was the main problem...

The K250 used a combination of software de-emphasis and compression to optimise its sampling which, whilst it sounded good, took time to process. Consequently, after sampling a four‑second sound at 50kHz, the K250 would say 'PROCESSING SOUND' for about five minutes before letting you play it on the keyboard and decide you didn't like it after all. This made 'sound modelling' on the K250 a long, drawn‑out affair, but believe me, in 1985 it was worth it!

'Buyer Collects' — A Second-hand Guide

Whilst few and far between, Kurzweil 250s still appear in the second-hand ads from time to time. I saw one advertised in this very magazine — "no serious offer refused" — as recently as June 1998. Beware, however, that the K250 is big. If Kylie were to lay on her back across one, her toes wouldn't quite reach the end (incidentally, that mental image will now remain with me for the rest of my life). Also, with the Pedal Pod power supply and optional Apple Macintosh, we are talking about a weight in excess of 100lbs (or 190lbs if you include Kylie).

If, however, you do find a second-hand K250, there are a few things to bear in mind. The individual outputs were not actually standard on all models — check the back for lots of holes. Also, the wooden keyboard could be a little unreliable, so try each and every one of the 88 notes to check for 'dead' keys; whilst fixable, this is not a trivial problem to solve. It's important to note that early 250s only had the 'Base Block' ROM (piano/strings/various) and (usually) Sound Block A (choir/woodwind/percussion) fitted, the other three Sound Blocks being optional. To check for the presence of Sound Block B (Contemporary Sounds), look for program 300, 'ROCK DRUMS 1'. To check for Sound Block C (Orchestral), look for program 400, 'SOLO VIOLIN' and for Sound Block D (Brass), program 600, 'SOLO TRUMPET'.

An American company called Sweetwater Sound also released two extra ROM Sound Blocks which, if present, should occupy locations 800-854 and 900-952 respectively. Finally, it's also worth checking whether the Sound Modelling Program is actually installed — there may be some early 250s without the user-sampling facility. From PLAY mode, press the INST button on the front panel. If the LCD display says "RECORD SOUND?" all is well. If nothing happens, the owner was a cheapskate and their 250 is playback-only.

So what should you pay for a Kurzweil 250 these days? In 1984, Syco Systems in London were selling the basic unit for £11,995; with optional Sound Blocks, individual outputs, library disks and the Macintosh hook-up, a complete system could be as much as £17,000. I've seen several K250s for sale over the past few years, mainly by studios who bought them as master keyboards, and they've all been around the £1500 mark. Now that the K2000/2500 has well and truly replaced the K250 series, I would have said that anyone asking in excess of £1000 is pushing their luck. And for that price, I'd want it delivered as well!

Published February 1999