SEM V · Armon.ai

How it works

The SEM was born as an expansion module: a small, complete synth without a keyboard, to be driven with CV/gate from another synth or a sequencer. Several SEMs side by side formed the first Oberheim polyphonic synths (Two, Four, Eight Voice).

Subtractive synthesis with a state-variable filter

Two VCOs with sawtooth and pulse (adjustable, modulatable width); oscillator 2 can sync to oscillator 1.
Mixer built into the filter: the VCO 1 and VCO 2 knobs choose the waveform (saw on the left, pulse on the right) and the volume (silence at center) in a single gesture.
State-variable filter, 2-pole (12 dB/octave): the same circuit produces low-pass, high-pass and band-pass simultaneously; the mode knob blends low-pass and high-pass passing through the notch (at center), while the band-pass is selected separately.
Two ADS envelopes: one for volume, the other for filter/oscillator 2. The Decay also sets the release time.
Sine LFO for vibrato and filter modulation.

Modulations are bipolar: turning left modulates the frequency, turning right (on the oscillators) modulates the pulse width, or opens/closes the filter in the positive or negative direction.

Character and tone

Timbre

Soft, “liquid” and musical: two simple oscillators (sawtooth and pulse) go through a 12 dB/octave state-variable filter that continuously morphs from low-pass to notch to high-pass, plus the band-pass. The sound is less aggressive than 24 dB filters and lets more harmonics through: airy, vocal, sometimes nasal.

Where it sits in the spectrum

Full between 80 Hz and 2 kHz but with more present highs than a Moog (thanks to the gentle 12 dB slope). The notch carves a “hole” in the spectrum that makes the sound wider when listening and leaves room for other instruments.

Strengths

Continuous multimode filter with musical resonance: timbres impossible with a low-pass alone (notch, band-pass, resonant high-pass).
Round basses and “fat” brass with very few controls.
In the Arturia version: polyphony, sub oscillator, LFO 2, arpeggiator, effects and above all the Voice Programmer, which gives each voice a different timbre as on the Oberheim Four/Eight Voice.

Limitations

ADS envelopes only (the decay also acts as release), a single LFO on the original.
12 dB filter: for very dark, “closed” basses a 24 dB filter is better suited.

Comparisons

vs Minimoog: the Moog is bigger and darker (24 dB ladder), the SEM more open, vocal and flexible in the filter.
vs OB-Xa: the OB-Xa uses Curtis 12/24 dB low-pass filters and is natively polyphonic; the SEM has more character in the filter and a more “vintage 1970s” sound.
vs MS-20: both have very distinctive filters, but the SEM is soft and musical, the MS-20 aggressive and dirty.

Architecture

Original (Oberheim SEM, 1974)

2 VCOs (sawtooth, pulse with variable width), sync.
2-pole state-variable filter (-12 dB/octave): continuous LP–Notch–HP control and band-pass, resonance, bipolar modulation.
2 ADS envelopes (ENV 1 to VCA; ENV 2 to filter and oscillators), 1 LFO, CV/gate inputs; the basis of the Two/Four/Eight Voice polyphonic synths with programmer.

Signal path (per voice)

VCO 1 (saw/pulse) + VCO 2 (saw/pulse) + Sub Osc/Noise (EXT) → 12 dB SV filter (LP-notch-HP or BP) → VCA (ENV 1) → soft clip and level → effects.

What Arturia adds (SEM V2, V Collection 9)

Polyphony up to 32 voices (Mono/Poly selector), 8 multitimbral boards.
Sub Oscillator (sine, saw or pulse at -1 or -2 octaves) and noise on the EXT knob.
LFO 2 monophonic (sine, saw, square) with Sync, Retrig, Fade In; LFO 1 can be synced.
Arpeggiator (Up, Down, Up/Down, Random; 1–4 octaves; Hold), Portamento, Tune 420–460 Hz, output Soft-clip.
Open Mode: Keyboard Follow (multi-point curves to 6 destinations), 8 Voice Programmer (offsets of 6 parameters for each of the 8 boards, with FWD/BWD/FWD-BWD/Random allocation), Modulation Matrix (pitch bend, mod wheel, velocity, aftertouch, LFO, envelopes → destinations).
Effects: Overdrive, Chorus, Delay.
Note: V Collection 9 contains SEM V2; the later SEM V3 (2025) is a different product with an expanded architecture, not included in V Collection 9.

The controls, one by one

VCO 1

Frequency: Oscillator pitch.
Modulation (bipolar): Left: frequency modulation depth; right: pulse width modulation depth; center (double-click): no modulation.
Mod source (ENV 1 / LFO 1 / LFO 2): VCO 1 modulation source: envelope for pitch sweep or envelope PWM, LFO for vibrato or cyclic PWM.
Pulse Width: Pulse width: at center a symmetrical square, toward the extremes an asymmetrical, more nasal pulse.

Sync

Sync (between VCO 1 and VCO 2): Forces VCO 2 to sync to VCO 1: modulating the frequency of VCO 2 gives sync timbres.

VCO 2

Frequency: Pitch; with Ctrl+click or right-click, fine adjustment for detuning.
Modulation (bipolar): Same as VCO 1: frequency on the left, PWM on the right.
Mod source (ENV 2 / LFO 1 / LFO 2): VCO 2 modulation source.
Pulse Width: VCO 2 pulse width.

VCF

Frequency: Filter cutoff (or center): the point the modulation 'returns' to.
Resonance: Emphasis at the cutoff (in notch mode it doesn't emphasize but widens/narrows the hole).
Modulation (bipolar): Cutoff modulation depth: positive opens, negative closes.
Mode: Filter type: low-pass, notch, high-pass, band-pass. As on the original, the knob continuously blends LP → Notch (12 o'clock) → HP; the band-pass is a separate mode.
Mod source (ENV 2 / LFO 1 / LFO 2): Filter modulation source.
Mix: VCO 1: Left = sawtooth, right = pulse; distance from center is the volume (silence at center).
Mix: VCO 2: Same as VCO 1 for the second oscillator.
Mix: EXT: Left = sub oscillator, right = noise; distance from center = volume.

ENV 1 (VCA)

Attack: Volume attack.
Decay: Decay toward the sustain and also the release time after the key is released.
Sustain: Held level (in dB).
Destinations: Always to the VCA; also a source for VCO 1 frequency/PW.

ENV 2 (modulation)

Attack: Modulation envelope attack.
Decay: Decay and release.
Sustain: Held level (with sustain at -60 dB and a long decay: a filter that closes like a clavinet).
Destinations: Filter cutoff and VCO 2 frequency/PW, chosen with the source selectors.

LFO 1

Frequency: Sine speed (per voice).
Sync: Syncs to the DAW tempo with ratios from 1/32 to 16 times.

Sub Osc

Wave: Sine, sawtooth or pulse.
Octave: -1 or -2 octaves relative to VCO 1 (it is not an independent oscillator).
PW: Sub pulse width.

LFO 2

Wave: Sine, sawtooth, square.
Rate: Speed; with Sync, ratios from 1/32 to 16 times the tempo.
Sync: Lock to the DAW tempo.
Retrig: Restarts the phase at the first note after all keys are released; when off, it runs free.
Fade In: Gradual fade-in of the amplitude after the key press.
Note: LFO 2 is monophonic (it modulates all voices together); LFO 1 is per voice.

Effects (main panel)

Overdrive / Chorus / Delay: on-off + dry/wet: Power and mix of each effect.
Overdrive: Drive, Damping: Amount of distortion and high-frequency cut at the output.
Chorus: Shape, Rate, Depth, Feedback, Spread, Delay, Tempo Sync: Sine or noise modulation, speed, depth, feedback, stereo width, delay time, sync.
Delay: Link, Time, Feedback, Ping Pong, Damping, Tempo Sync: Equal L/R times, time, repeats, stereo bounce, tone of the repeats, sync.

Output

Level: Master volume from -80 to +24 dB (watch out for clipping).
Soft-clip: Light saturation from an analog output stage, extra warmth at high levels.

Arpeggiator

On / Hold: Turns on the arpeggio; in Hold it continues after release until the next chord.
Mode: Up, Down, Up/Down, Random.
Rate + Sync: Free or tempo-synced speed.
Octave: From 1 to 4 octaves.

Tune and Portamento

Tune: Master tuning A = 420–460 Hz.
Portamento On/Off + Time: Glide from 0 to 2000 ms.

Bottom bar

Mono / Poly: Monophonic like the original or polyphonic.
Max Polyphony: From 1 to 32 voices.
MIDI Channel: Receive channel.

Open Mode: Keyboard Follow

Global and per-parameter On/Off: Turns on the module and each of the 6 curves.
Breakpoints: 5 points by default (up to 32); click to add, right-click to remove.
Linear / exponential curve: Handles between the points.
Destination (right-click on the column): Parameter controlled by note position (e.g. cutoff, decay, resonance).

Open Mode: 8 Voice Programmer

Global and per-parameter On/Off: Turns on the module and each of the 6 rows.
Board 1–8: Number of multitimbral 'boards' active in polyphony.
Barline: Positive or negative parameter offset for each board relative to the panel.
Destination: Parameter of each row (right-click).
Allocation (FWD / BWD / FWD BWD / RANDOM): Order in which notes use the boards.

Open Mode: Modulation Matrix

Source: Pitch bend, mod wheel, velocity, aftertouch, LFO, envelopes.
Amount: Bipolar amount (center = zero).
Destination: Destination parameter; one source can go to several destinations and vice versa.

Sound design tips

Filter

Notch and band-pass as mixing tools: a fixed notch around 800 Hz–1.5 kHz gives a “scooped” pad that leaves room for the voice; a band-pass at 1–2 kHz lets a bass sit in a full mix even on small speakers.
Mode as modulation: slowly moving the Mode knob (or modulating it from the matrix) between LP and HP creates a unique timbral movement, more organic than a simple cutoff sweep.
Resonance at 12 dB: it is gentle and doesn't hollow out the lows like a 24 dB filter; you can use more of it (40–60%) on basses and brass.
Modulation vs Frequency: high positive modulation with low Frequency for bright attacks; with negative modulation raise the Frequency, otherwise you won't hear anything.

Envelopes (ADS)

The Decay is also the release: for short notes with a tail, use medium Sustain and medium Decay; for plucks, Sustain at minimum and Decay 150–400 ms.
Release and tempo: since decay = release, for slow pads at fast tempos (>120 BPM) a Decay over 1 s smears the chord changes.
ENV 2 with an attack of 20–100 ms and a Decay of 100–300 ms on the filter is the basis of the SEM brass.

Oscillators and frequencies

Use the Mix knob to choose saw or pulse instead of adding both oscillators at full level: one saw VCO and the other a narrow pulse detuned by 3–6 cents gives body without mud.
The sub at -1 octave sine reinforces 40–100 Hz cleanly; at -2 octaves it is easy to go below the useful range (below 30 Hz energy is wasted).
The 12 dB filter lets highs through: if a lead stabs, lower the Frequency or use the Overdrive with high Damping.

Polyphony and Voice Programmer

The Voice Programmer with small offsets (detune, cutoff, PW) imitates the Four/Eight Voice, where each module sounded slightly different: more natural than a unison.
LFO 2 is common to all voices (“block” effect), LFO 1 is per voice: for lively pads use LFO 1.

Velocity, glide, keyboard follow

Velocity → filter Frequency in the matrix (moderate amount) for basses that “speak” under the fingers.
Keyboard Follow on cutoff with a slightly exponential curve: bright high notes without dark lows.
Portamento 30–80 ms for legato funk basses; beyond 200 ms it is an effect.

Common mistakes

Mix knobs at center: the oscillator is muted.
Output level above 0 dB with Soft-clip: unintended distortion.
Oscillator modulation left to the right (PWM) when you wanted vibrato.

Presets to recreate

SEM Brass

Brass · 1970s rock and AOR

The soft, fat synth brass typical of 1970s Oberheim: two saws through the 12 dB filter and small differences between voices with the Voice Programmer.

Oscillators: VCO 1 Frequency 8', Pulse Width at center; VCO 2 Frequency 8' with fine tuning +5 cents; Sync OFF.
Mixer: Mix VCO 1 fully left (sawtooth, full volume), Mix VCO 2 fully left (saw), EXT at center (muted).
Filter: 12 dB/oct state-variable VCF in low-pass Mode, Frequency 35%, Resonance 30%, Mod source ENV 2, Modulation +80%.
Filter envelope (ENV 2): Attack 50 ms, Decay 300 ms, Sustain -12 dB.
Amplitude envelope (ENV 1): Attack 15 ms, Decay 400 ms (also acts as release), Sustain -2 dB.
LFO and modulation: LFO 2 sine 5 Hz with Fade In 0.5 s to VCO 1 and VCO 2 via mod wheel, for vibrato.
Voice and glide: Poly with 8 voices, Portamento 0; Voice Programmer with small detune and filter Frequency offsets between boards.
Effects: light Chorus (Depth 30%, dry/wet 20%), Delay OFF, Overdrive OFF.

Funk notch bass

Bass · Funk, deep house

Round, talking bass with the filter positioned between low-pass and notch, for funk and house.

Oscillators: VCO 1 Frequency 8', Pulse Width 40%; VCO 2 Frequency 16' (one octave down); Sub Osc sine -1 octave.
Mixer: Mix VCO 1 right (pulse) at 70%, Mix VCO 2 left (saw) at 60%, EXT left (sub) at 40%.
Filter: Mode between LP and Notch (10 o'clock), Frequency 30%, Resonance 45%, Mod source ENV 2, Modulation +60%.
Filter envelope (ENV 2): Attack 0 ms, Decay 220 ms, Sustain -30 dB.
Amplitude envelope (ENV 1): Attack 0 ms, Decay 300 ms, Sustain -6 dB.
LFO and modulation: matrix Velocity → VCF Frequency +30%.
Voice and glide: Mono, Portamento ON at 40 ms.
Effects: light Overdrive (Drive 20%, Damping 50%); Chorus and Delay OFF.

SEM Clavinet

Keys / Pluck · 1970s funk

Percussive clavinet-style sound: narrow pulse and a filter that slowly closes again with sustain at minimum.

Oscillators: VCO 1 Frequency 8', Pulse Width 10% (narrow pulse); VCO 2 not used.
Mixer: Mix VCO 1 fully right (pulse), Mix VCO 2 at center (muted), EXT at center.
Filter: low-pass Mode, Frequency 30%, Resonance 25%, Mod source ENV 2, Modulation +70%; Keyboard Follow on VCF Frequency with a rising linear curve.
Filter envelope (ENV 2): Attack 0 ms, Decay 2 s, Sustain -60 dB.
Amplitude envelope (ENV 1): Attack 0 ms, Decay 100 ms, Sustain -7 dB.
LFO and modulation: none.
Voice and glide: Poly with 8 voices, Portamento 0.
Effects: Chorus OFF; Delay 1/16 (Feedback 15%, dry/wet 15%).

Airy band-pass pad

Pad · Ambient, electronic

Light polyphonic pad in band-pass, leaving the low register free.

Oscillators: VCO 1 Frequency 8', PWM with Modulation to the right +30% from LFO 1 at 0.5 Hz; VCO 2 Frequency 8', fine tuning -5 cents.
Mixer: Mix VCO 1 right (pulse) at 70%, Mix VCO 2 left (saw) at 60%, EXT muted.
Filter: band-pass Mode, Frequency 50%, Resonance 20%, Mod source LFO 2, Modulation +15%.
Filter envelope: not used (the movement comes from LFO 2).
Amplitude envelope (ENV 1): Attack 600 ms, Decay 1.5 s, Sustain -3 dB.
LFO and modulation: LFO 1 0.5 Hz on the PWM; LFO 2 sine 0.1 Hz with Fade In 2 s on the filter.
Voice and glide: Poly with 8 voices, Portamento 0.
Effects: Chorus (Spread 80%, dry/wet 30%) → ping-pong Delay 1/4 (Feedback 30%, dry/wet 20%).

Sync lead

Lead · Fusion, progressive rock

Monophonic lead with sync and an envelope pitch sweep on VCO 2.

Oscillators: VCO 1 Frequency 8' (master); VCO 2 Frequency 8' +7 semitones, Sync ON, Mod source ENV 2 with Modulation left 50% (frequency).
Mixer: Mix VCO 2 fully left (saw), Mix VCO 1 left at 30%, EXT muted.
Filter: low-pass Mode, Frequency 60%, Resonance 15%, Mod source ENV 2, Modulation +20%.
Filter envelope (ENV 2): Attack 0 ms, Decay 500 ms, Sustain -20 dB.
Amplitude envelope (ENV 1): Attack 5 ms, Decay 300 ms, Sustain -1 dB.
LFO and modulation: matrix Mod Wheel → LFO 1 (5.5 Hz) on the VCO frequency for vibrato; Aftertouch → VCF Frequency +15%.
Voice and glide: Mono, Portamento 50 ms.
Effects: Overdrive (Drive 15%) → Delay 1/8 (Feedback 25%, dry/wet 20%).

Stranger Things — main arpeggio

Arp · Kyle Dixon & Michael Stein — Stranger Things (theme) (2016)

The hypnotic arpeggio that drives the Stranger Things theme. On the original, Kyle Dixon and Michael Stein play it on an Oberheim SEM Two Voice, with additional arpeggios from a Korg Mono/Poly; the bass is a Roland SH-2, the pads come from a Prophet-5, Prophet-6 and Prophet VS. Here with the SEM V.

Oscillators: VCO 1 Frequency 8', Pulse Width at center; VCO 2 Frequency 4' (one octave up); Sync OFF.
Mixer: Mix VCO 1 fully left (saw), Mix VCO 2 between saw and pulse at 50%, EXT muted.
Filter: low-pass Mode 12 dB/oct, Frequency 40%, Resonance 50%, Mod source ENV 2, Modulation +45%.
Filter envelope (ENV 2): Attack 0 ms, Decay 250 ms, Sustain -30 dB.
Amplitude envelope (ENV 1): Attack 0 ms, Decay 300 ms, Sustain -10 dB.
LFO and modulation: no LFO; move the filter Frequency by hand during the track.
Voice and glide: 2-voice Voice Programmer (like the Two Voice) or Mono, Portamento 0; Arpeggiator On, Mode Up, Rate synced 1/16, Octave 2, Hold on a major chord.
Effects: Delay 1/8 (Feedback 20%, dry/wet 15%); long, dark reverb on a send.

In genres and records

1970s jazz-funk and fusion: the SEM is among the instruments of Jan Hammer and Joe Zawinul (Weather Report); the Oberheim Four Voice polyphonic synths, built from several SEMs side by side, are used by Herbie Hancock, Chick Corea, George Duke, Lyle Mays (Pat Metheny Group) and Bob James. Basses and leads.
Progressive rock and AOR: Dennis DeYoung (Styx), Geddy Lee (Rush), Steve Porcaro (Toto), Rick Davies (Supertramp) and Patrick Moraz play Four Voice synths. Brass and leads.
Soul, funk and pop: Stevie Wonder uses the first Four Voice prototype; Four Voice users include Prince, Earth, Wind & Fire (Larry Dunn), Michael McDonald (Doobie Brothers), Fleetwood Mac (Christine McVie) and the Brothers Johnson.
Electronic music and soundtracks: Jean-Michel Jarre, Edgar Froese (Tangerine Dream), Vangelis and John Carpenter. Kyle Dixon and Michael Stein use a SEM Two Voice for the main arpeggio of the Stranger Things theme.
Synthpop and new wave: Depeche Mode, Vince Clarke, The Human League (Philip Oakey) with Four Voice synths. Soft basses and brass.
House, deep house and techno: basses and stabs with notch or band-pass filter, percussive plucks.
Synthwave and retro: brass and polyphonic pads with a 1970s color.
Hip hop, G-funk and R&B: soft leads and round basses.
Sound design and film: modulated multimode filter, a different timbre per voice with the Voice Programmer.