Kurzweil K-250 (1984)
Ten thousand dollars, eighty-eight weighted keys, and a Steinway in a box.
Overview
The name is a mess, so get it out of the way first. Period sources flip between "Kurzweil 250" and "K-250," and the company itself used both. What the thing did is not ambiguous. Kurzweil Music Systems introduced the 250 at the 1984 NAMM show at $10,395, which in 1984 dollars was small-car or very-good-used-grand-piano money. That was rather the point. This was the instrument that put Kurzweil on the map, and it was the first electronic instrument with a weighted, 88-note hammer-action keyboard. Not a synth-action compromise, not a five-octave slab. A full piano keyboard, weighted, with velocity and aftertouch.
The sound engine is where the real argument starts. The 250 was built around 12-bit samples of real acoustic instruments, stored on floppy disks in a proprietary format. Its headline sample was a 9-foot Steinway concert grand, multisampled into a 42MB sample ROM. Forty-two megabytes. In 1984. Collectors who have opened these things up describe a small mainframe's worth of sample data crammed into a keyboard chassis. The 12-bit sample technology was developed with assistance from Stevie Wonder, which sounds like marketing until you remember that Wonder was genuinely deep into synthesizer R&D in that period.
Keyboard magazine is credited with coining the term "rompler" for exactly this kind of machine — a synth that plays back ROM-based samples rather than synthesizing waveforms — and the 250 is the machine that earned the word. It is the first rompler, full stop.
Twelve-voice polyphony sounds laughable now. In 1984, playing a twelve-note chord on a weighted 88-key board with a sampled grand underneath it was not laughable at all. It was the thing everyone else was trying to figure out how to do. The on-board library spanned grand pianos, electric pianos, strings, and brass, among other sounds, which made the 250 a studio fixture.
Key Features
88-Key Weighted Hammer-Action Keyboard with Velocity and Aftertouch
This is the feature that changed the category. Before the 250, electronic keyboards were synth-action or semi-weighted at best, and a pianist sat down at one and felt the difference immediately. Kurzweil put a weighted, hammer-action 88-key bed under the samples, with velocity and aftertouch. That made the case that an electronic instrument could be a piano first and a synthesizer second. Every workstation that followed, from every manufacturer, owes something to this decision.
12-Bit Samples and the 42MB Steinway ROM
The engine played back 12-bit samples of real acoustic instruments, with the flagship being that multisampled 9-foot Steinway concert grand in a 42MB sample ROM. Twelve bits is a modest word length by any later standard, and owners have always been honest that the pianos can sound a touch dull next to later generations. But the 250's trick was never resolution for its own sake. It was the depth of the multisampling, the number of velocity layers and the care taken with the source recordings. The result was a piano that, in blind tests, reportedly fooled working professionals.
Velocity Crossfading and a Pair of LFOs per Voice
According to available documentation, the 250 offered velocity crossfading of samples, which blends between sample layers based on how hard a key is struck rather than simply switching between them. It also had a pair of LFOs per voice. That per-voice allocation means modulation resources scale with polyphony instead of being shared across the whole keyboard.
256-Stage Envelope Generator
Keyboard magazine (May 1994) referenced the 250's 256-stage envelope generator years after the instrument's release, which tells you something about how far ahead of the curve the modulation architecture was. A 256-stage envelope is not a three-knob ADSR; it's a programmable contour, and it's the kind of spec that explains why the 250's sounds had a reputation for behaving like instruments rather than like samples.
Built-In 8-Track Sequencer
The 250 shipped with a built-in 8-track sequencer with a 33,000-note capacity, expandable to 100,000 notes with the KDS option. Sources also describe a 12-track sequencer with storage for up to 40 songs. The discrepancy likely reflects different firmware revisions or option configurations, so treat the exact track count as version-dependent. Either way, this was a self-contained composition tool. "Completed in 1984, the Kurzweil K250 allowed a single person to compose and play an entire orchestral score" is how one source puts it.
5¼-Inch "Quad" Density Floppy Drive
Sounds and data lived on 5¼-inch "Quad" density floppy disks in a proprietary format. The drive is a maintenance item today. Floppy mechanisms of this vintage need belts, cleaning, and occasionally alignment. But the disks are also the reason the 250's library was expandable in an era when ROM cartridges were the norm. User sampling was available through an optional interface, so the 250 was both a playback instrument and a sampling instrument.
Twelve Separate Outputs (Option)
Kurzweil's own advertising in Mix (October 1988, p.74) made a point of the option of having twelve separate outputs for unprecedented versatility in using the K250 voices. That let individual voices go to separate console channels for independent processing. For a studio instrument, that is the difference between a stereo keyboard and a multi-timbral source you can actually mix.
RAM Cartridges and the Expanding Library
That same Mix campaign, "programmed for everything but obsolescence," noted RAM cartridges that vastly extended the 250's memory and a ninth sound library, with more on the way. The cartridge system is why a 1984 instrument was still being supported with new sounds in 1988.
The Cooling Fan
Owners report the internal cooling fan is very noisy. One French service write-up calls it too noisy, and describes a technician running the unit with the power supply open during repair and simply not reinstalling the fan afterward. That tells you how loud it is. It's also a caution: the fan is there for a reason, and pulling it permanently is a gamble on the power supply's thermal margins.
Historical Context
The 250 was introduced at the 1984 NAMM show at $10,395, and it is the instrument that put Kurzweil Music Systems on the map. It was described at the time as the first combined live performance and studio electronic musical instrument which produced sound derived from sampled sounds. In plain terms, that means one box, stage and studio, real instrument samples. A limited-edition "black face" version was also produced.
The instrument's cultural footprint was unusually large for a keyboard at that price. It went on a worldwide tour with prestigious orchestras including the New York Philharmonic, and in 1986 Kurzweil presented the instrument with the entire Boston Pops orchestra playing a piece by John Williams. Depeche Mode's Alan Wilder used a K-250 as his master keyboard on the 1986 "Black Celebration" tour, and it appeared again on the 1990 album Violator, on the track "Waiting for the Night." Sources also name Keith Emerson, Herbie Hancock, and Eric Clapton among users. That claim appears in a single source and should be treated accordingly.
The 250 originally shipped with a 3-year warranty, which for a 1984 digital instrument was a strong statement of confidence.
Similar items on eBay
No exact Kurzweil K-250 listings are live right now — these searches show current Kurzweil and similar vintage synth gear on eBay:
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.