Sequential Circuits Prelude

Extremely simple to use--it's an analogue synthesizer, and not a terribly sophisticated one. There's one control per function comprising 18 sliders, 14 toggle switches, 8 buttons, and a master tuning knob. All the controls are laid out logically and boldly labeled.
I bought mine used; a manual was not included, but it's hardly necessary.

It has full 49-note polyphony (I would venture an educated guess that it is based on the same divide-sown circuitry as tonewheel organs) and is fully multitimbral--all four sections can be active at once (by pressing more than one of the Program Select buttons simultaneously), although the organ tends to dominate and the piano tends to get swallowed up by whatever they are combined with.

There is a lever for pitch bending with a set range of +/- 6 semitones. There is thankfully a detent at the middle of its throw, although that makes it completely useless for manual vibrato.

The Modulation section is comprised of chorus/flange and an LFO. The chorus is lovely, exceptionally warm and wet, and at high settings the flanger can sound very cold and resonant. The LFO has controls for Speed, Depth and Delay, and can run from around 1.5Hz (I would've liked it to go a bit slower) to well into audible range, I'd guess around 30Hz--this feature is great for gritty, vaguely distorted tones.
There is also a 5-band EQ with a dry/wet slider. I haven't played with it very much to be honest, but it does its job. I would have preferred a proper filter.
There is an input in the back for processing external sources through the chorus and EQ; plugging in my telecaster sounded awfully "Come as You Are"-esque.

The keyboard action is rather poor, but usable; either way, you're stuck with it--there is no midi (I think it predates the spec by a year or two) or other external control of any kind, although there are inputs for a volume pedal (which looks like a 5-pin DIN socket) and a sustain pedal. The sustain pedal operates in an interesting way--rather than causing the sound to sustain endlessly, the volume drops slightly when keys are released and eventually dies away similarly to an acoustic piano.

There are four sections--brass, piano, organ, and strings None (with the arguable exception of the strings) sound at all convincing for the sounds they aim to emulate, but each section does sound good in its own way.
Unfortunately, there seems to be only one envelope each for the brass, strings, and LFO, so they don't retrigger unless all notes are released. This is not without its usefulness, but I usually find it irritating. I suppose it adds to the instrument's character.

The brass section has 2 tones, an octave apart; there are two sliders, one labeled Attack which actually controls both the attack and decay time of an envelope applied to the filter cutoff; and one for the filter cutoff. There are also switches for "swell"--a secondary attack stage for sforzandos--and resonance. The resonance has a squelchy, nasal characteristic which I like quite a lot, although it's probably not for everybody. Unfortunately, as it has a toggle switch, filter resonance is of a set value, either on or off.

The piano section has a decay control and three tones--Piano 1, Clav, and Piano 2. Piano 1 is obviously meant to emulate a grand piano and is actually extremely good as subtractive synthesis goes (which isn't saying much, I know), especially in the higher registers (although it's a little dark for my taste overall). Clav is worthless--two octaves too high, and without any body at all. Piano 2 has kind of a thin, honky-tonk kind of sound. It really sounds barely anything like a piano, but it's sort of a nice tone in its own right--it kind of reminds me of any number of plucky Juno sounds.

The organ section has Pipe, Organ 1, and Organ 2 tones, and no other controls. None sound even remotely like organs, however organ 1 and/or two are terrific for big, nasty sawtooth sounds (think "Jump"). I don't care much for the pipe organ--too bright, and again, at least an octave too high--but it reacts well to external effects, particularly reverb.

Naturally, the strings are the best feature, very bright and full. There are controls for attack and release, toggles for "mute" (a static lowpass filter. I prefer to leave this engaged) and "percussion" (which causes the sound to decay instantly. Might be better labeled pizzicato). There is a tone for cello and violin, an octave apart from each other.

The keyboard does not respond to velocity or aftertouch, which is really a shame, because velocity sensitivity in particular would be a fantastic appointment.

As I mentioned, I bought mine used about half a year ago; the E3 and Bb3 keys do not work for the Brass and Organ voices, and a few of the sliders are a little scratchy, but all in all it seems to be in fairly good condition for an analogue electronic instrument made a quarter of a century ago.
Otherwise, it seems solidly built and the tuning is very stable--I haven't had to tune it since I bought it.
I have not used it live yet, but I would have no reservations about doing so.

I paid something around $140 for mine, and it's certainly worth that, although more than $200 would be a little excessive. I would probably buy another if mine went missing, assuming I could find one.

I've been playing keyboards for about six years, although I am primarily a guitarist. I also own an Alesis Quadrasynth+ and Ion, a Yamaha DX5, and and E-mu ESI-32 sampler as well as loads of software--the Prelude is my only analogue.

In most respects, it does what it is meant to very well (envelopes notwithstanding), and little else. It's got a unique sound which I enjoy and it's simple and immediate to use.

Original - and only? - version. A 4-in-1 synth-cum-organ, with 4 basic sounds: Organ, Brass, Piano and Strings. There are various sliders and swiches to change/combine the preset sounds, mainly attack and decay.

Organs a pretty good ("Pipe Org". is esp. good with reverb) Forget the brass. Pianos obviously don't sound like pianos, but are usable. Strings are very analogue-sounding

Very easy to operate - what you see is what you get. No patch editor....manual is very basic, but does include suggestions for new sounds.

I believe it's 48 or 49 note polyphonic, meaning you can play HUGE chords/clusters or have really long cut-off free decays. YES, there are built in effects - a warm Chorus with individual Amount and Flange controls. There's also a 5 band EQ with dedicated "EQ Mix" amount. You can get some great retro stings using the the Attack/Release, Chorus and EQ controls.

Plus the strings can be played as a "section" by combining "Violins" and "Cellos" which are an octave apart. There's also "Mute" and "Percussion" switches which help you shape the string sound further.

External sounds can be fed through both the Chorus and the EQ.

No MIDI. Keys not velocity sensitive. Action is quite playable however.

Strings are not bad - but I think there's only 1 EG, meaning if you hold down one key then press another, you don't get the envelope shape - it just "switches on". But if you play single note lines, especially with super long decays, it has an effect unlike your typical 6/8 voice analogue synth.

Actually, it's almost worth getting this synth so you can do a full keyboard glissando on an analogue string sound and not get any cut-off.

The fun begins when you COMBINE sounds, play with the EG, EQ them, add Chorus/Flange, PLUS it has a cool LFO (whose rate can be extremely fast!!) All 4 sounds can be play simultaneoulsy.

This keyboard is meant to played and tweaked, not hooked up to a computer. If you are into the former, look out for one. You won't be dissapointed.

Bought mine used. I've never gigged with it, but it's over 20 years old, built like a tank and still going strong. I wouldn't use it on a gig - I usually get hired as a pianist.

I think SCI has changeg names now........something to do with "Wine" I think.

My life changed back in 1976 when I heard Tomita's "Snowflakes are Dancing". Perhaps the biggest compliment I can make is that this axe wouldn't be out of place on that album (especially the strings) I have many a synth including a Polivoks, Aelita, MKS 70, Prophet 600, Paia Proteus, Chroma Polaris, Akai AX 80, JP 8000, JX 8/3P, Moog Prodigy, D550....

I have played some Bach Preludes on the "SCI Prelude" and they seemed to be a pretty good match!

Haven't seen too many of these babies around. Not a bad addition to ones collection IMHO. Just don't pay too much for it.