Kurzweil 150 FS Fourier Synthesizer SN 8706 0051

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You can find info on the Kurzweil 150 FS in previous posts here.

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Kurzweil K150 FS Synth Rack

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"Kurzweil K150 Fourier Synth Rack from 1986. If you are not familiar with the K150, it was Kurzweil’s only module to use additive synthesis, much like the Sequential Circuits VS [the Prophet VS was not additive - see Robbie's notes in the comments]. It comes loaded with 69 presets sounds in memory so you won’t have to start from scratch. It also comes with the FS-SMP Fourier Synthesis modeling program written by Hal Chamberlin."

Update via Richard Lainhart: "i used to own a K150, back in the 80s. It was a wonderful-sounding instrument, but I was never able to really program my own sounds because the modeling program mentioned in the description runs only on an Apple IIe, which was already obsolete in the mid-80s. I sorta got it to work in a IIe emulator running on my Mac Plus, but the modeling app was crippled running in the emulator, and too limited for real work. The 150 had many excellent preset sounds, and featured a number of alternate tuning tables.

I believe Wendy Carlos also used one of these, and I'd heard she got a IIe specifically to run the app. She also, if I recall correctly, designed some of those alternate tunings.

For those interested, several of the tracks on my second, unreleased Periodic Music album called "Walking Slowly Backwards" feature the FS150, in particular, a piece called "The Naga" in which the lead voice is the 150 controlled with a Lync LN-4, using (I think) one of Carlos' alternate tunings.

You can listen to those tracks here on my site:

http://www.otownmedia.com/he/walkingslowlybackwards.htm"

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Kurzweil K150

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"It features real time additive synthesis with 240 oscillators, 16 voice polyphony, upwards of 240 oscillators and extensive programmability. The K150 implements a unique editing method in which you mix, combine and alter the 150's 22 resident voices and 69 preset programs. You basically manipulate sounds on a harmonic level for creating various new timbres. With extensive layering effects and abilities you can get some thick and unique sounds. There's 186 patches for memory storage and you can get up to 255 when you remove the installed sound blocks or overwrite presets.

The Fourier Synthesis (FS) is an upgrade (included in this device) to the standard K150 which allows you to define new instrument models by editing their velocities and envelopes, tuning intervals and more further expanding creative and unique sound synthesis potential.

Everything is modifiable and controllable about this synth. Pitch bending, vibrato, EQ, chorusing, polyphonic after-pressure and full 16 channel MIDI implementation with almost everything being MIDI controllable.

You can have up to 3 keyboard regions with up to 7 layers for each region for all sorts of splits/stacks/velo switches and so on. For every layer you can select one of the low-level instrument models and then globally assign controllers, set up the very flexible pitch LFO, add chorus/delay effects (not via DSP but by stacking up voices) and apply timbre shifts.
I find the parameters offered quite nice and very "musical": e.g. the response to attack velocity and the timbre is nicely adjustable - even via MIDI CCs if you like. Together with a fader box and maybe an arsenal of pedals, switches, joysticks and wheels you can do what the terminology implies: adjust an instrument to the musical context or playing style. It is really a fun to play expressively.

The sound hardware uses a 16 bit DA converter at about 20 kHz. The rolloff of the anti aliasing filter is rather smooth but the instrument models may compensate for this. Main CPU is a 10MHz 68000.

The user interface is - well - usable. The one line display and the OS have their limits but after a few days you get everywhere with a few button pushes. What leaves most other synths way behind is that all parameters are in real units: semitones, cents, dB and Hertz. This adds up to the general impression that someone was really trying to do it right.

Polyphony - 16 voices
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Oscillators - 240 osc! (sine and noise)
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LFO - Yes
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DCF - Yes
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DCA - 256 stage envelopes
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Keyboard - None (rackmount)
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Memory - 186 patches (up to 255)
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Control - MIDI (16 parts)
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Date Produced - 1986"