Introducing the Model IV
Eight voices under ten fingers.
The first Polyphon that plays chords the way you hear them — instantly, in tune, and in walnut. Flip the power switch below. This page is the instrument.
OSCILLATORS
FILTER
LOUDNESS
MODULATION
ECHO
OUTPUT
FACTORY VOICES
Fig. 1The Model IV demonstrator, fully operative. Sound requires flipping POWER — your browser insists a person asks first, and frankly, so do we.
01 Two oscillators, one opinion
Every one of the Model IV's eight voices carries two discrete oscillators, each offering sawtooth, square, and triangle waves at the flick of a lever. Detune them a few cents and the instrument breathes; lock the second oscillator a fifth or an octave away and it squares its shoulders.
Tuning drifts less than one cent per hour after warm-up. We know because Mr. Halvorsen in final test will not release a unit until it does.
02 The ladder, tamed
Our four-pole lowpass filter descends at 24 dB per octave, which is a polite way of saying it closes like a bank vault. The EMPHASIS control feeds the output back to the input until the filter begins to sing along — a trick borrowed from nobody, thank you.
A dedicated contour generator strikes the filter with every key, adjustable from harpsichord-brittle to gale-slow with the SHAPE control.
03 Echo, on tape's terms
The onboard echo section is a bucket-brigade device: your note handed down a line of 4,096 capacitors like a fire brigade passing water. It darkens a little with every repeat, exactly the way tape does and transistors ordinarily refuse to.
Turn REGEN past two o'clock and the brigade starts passing buckets back up the line. We are legally obliged to mention this. We are personally delighted by it.
04 Eight voices, no waiting
Play a chord and the Model IV deals a complete voice — oscillators, filter, envelope — to each finger, instantly. Play a ninth note and the instrument quietly retires whichever voice you'd miss least. You will not hear the seam. Our patent attorney assures us you will not find it either.
The loudness contour is a full ADSR, and every stage moves exponentially, the way real instruments decay and lawyers don't.
“A synthesizer should be played, not programmed. If it takes longer to find a sound than to lose your nerve, the instrument has failed you.” Henrik Ostrander, founder
- Keyboard
- 49 keys, F to F. This demonstrator presents the central two octaves, C3–C5.
- Polyphony
- Eight complete voices; last-note priority with graceful voice retirement
- Oscillators
- Two per voice — sawtooth, square, triangle; 0–30¢ spread detune; second oscillator lockable at −12 or +7 semitones
- Filter
- Voltage-controlled lowpass, 24 dB/octave, 40 Hz – 12 kHz, variable emphasis to self-oscillation
- Envelopes
- ADSR (loudness), exponential segments; AD contour (filter), 30 ms – 2 s
- Modulation
- Triangle LFO, 0.05 – 12 Hz, switchable to oscillator pitch or filter cutoff
- Echo
- Bucket-brigade delay, 60 – 750 ms, regeneration to runaway, wet/dry blend
- Connections
- Two ¼″ phone outputs (high and low level); stereo headphone jack; sustain footswitch
- Construction
- Hand-oiled American walnut end cheeks; brushed 6061 aluminium faceplate; steel chassis
- Power
- 117 V a.c., 40 watts. Two-year parts and labour warranty, honoured with apologies
- Dimensions
- 33½ × 14 × 5 in. · 38 lb crated
- Price
- $2,795 f.o.b. Pasadena · walnut music desk, $45
From the collection
POLYPHON MODEL IV
Polyphon Instrument Corporation · Pasadena, California · 1974
Walnut, brushed aluminium, injection-moulded polystyrene, solid-state circuitry. One of an estimated 1,140 units built before the company's quiet closure in 1979. The Model IV's eight-voice architecture predated its famous rivals by two full seasons; its echo section, engineers later admitted, was tuned entirely by ear in a stairwell.
On loan from the Meridian Collection of Electronic Instruments · Gallery 3, Case 7