Sequencing & Clock

SEQ8

The 8-step CV/gate sequencer — the melodic and rhythmic heart of nearly every modular patch since the 1960s.

What is a SEQ8?

A step sequencer is the most direct way to write music in a modular synthesizer. It is, at its core, a row of knobs and a clock-driven step counter that points at one knob at a time. Each clock pulse advances the counter. The voltage of whichever knob the counter is currently pointing at gets sent out the CV output, where it usually drives the 1V/Oct input of a VCO. The result is a melody — eight notes, looped, each note one knob.

The other essential output is the gate. Every step has a gate toggle: on means "play this note", off means "this step is a rest". The gate output goes to an ADSR envelope, which shapes the note's volume, which feeds a VCA. So the sequencer doesn't just choose pitches — it also decides when notes start, when they stop, and which steps are silent.

The lineage goes back to 1968: the Moog 960 Sequential Controller and the Buchla 245 of the same era both used a three-row, eight-step layout. Three rows means three independent CV outputs sharing one step counter — Row 1 typically carries pitch, Row 2 carries filter cutoff (so the timbre changes per step), Row 3 carries anything else (decay time, panning, second oscillator pitch). The architecture has been copied virtually unchanged for fifty-five years because it works.

More elaborate sequencers add runs (repeated steps), ratchets (multiple gate fires per step), per-step probability, and chained patterns — but the fundamental thing, the row of knobs and the step pointer, is what makes a sequencer a sequencer. Patch a clock to its CLK input and the rest follows.

Our SEQ8

Our SEQ8 is a 24 HP, three-row, eight-step sequencer with everything a classic A-155 / Moog 960 layout asks for, plus a few modern affordances. The three CV rows (Row 1, Row 2, Row 3) each output independently and span -10V to +10V per knob. The gate pattern is the 8-bit bitmask convention: one knob, 0-255, where each bit toggles a step's gate.

There is an internal clock (20-300 BPM) so SEQ8 can stand alone, but patching anything into the CLK input overrides it — we detect the patch automatically, so the moment you connect a master clock, internal timing yields without a switch. The STEPS knob (and matching CV input) is 1-8, so you can shorten patterns on the fly for polymetric tricks.

Modern conveniences we added: a dedicated TRIG output (1 ms pulse per advance to a gated step) for S&H and other event gear, a clock pass-through (CLK out fires on every advance regardless of gate pattern, for chaining sequencers), glide for portamento, and eight per-step gate outputs (S1-S8) so individual steps can drive specific events — cymbal crash on step 4, sample trigger on step 7, anything you want.

In a patch

The standard wiring: clock → sequencer CLK, sequencer Row 1 → VCO V/Oct, sequencer GATE → ADSR gate, ADSR → VCA CV, VCO → filter → VCA → output. That is a complete, classic synthesizer voice driven by an eight-step pattern.

The second and third rows unlock per-step variation. Row 2 → filter cutoff makes the timbre change with the melody. Row 3 → ADSR decay creates rhythmic accenting (some notes pluck, others sustain). Patch the sequencer's clock-out to a clock divider to drive a second sequencer at half speed for call-and-response melodies, or run two sequencers off the same clock with different lengths for evolving polymetric patterns.

For pitches that always stay in key, route Row 1 through a quantizer. For more random-feeling rhythms over the same melody, replace the GATE output with the gate output of a Euclidean rhythm generator while still using the sequencer's CV.

Inputs

CLK (gate) — External clock input. Each rising edge advances the sequence by one step. When patched, overrides the internal clock.
RST (gate) — Reset input. A rising edge sends the sequence back to step 1. Patch a Clock's reset output here to keep things synced.
RUN (gate) — Run/stop CV input. High voltage = running, low = stopped. Overrides the panel Run switch when patched.
STEPS (cv) — CV control for sequence length. Modulates the Steps knob. Useful for live variation - patch an LFO here to dynamically change pattern length.
R1 CV (cv) — CV offset added to all Row 1 values. Transpose your melody by patching a quantizer or knob CV here.
R2 CV (cv) — CV offset added to all Row 2 values. Shift all Row 2 modulation values up or down.

Outputs

ROW1 (cv) — Row 1 CV output. Outputs the current step's Row 1 knob value (plus any R1 CV offset). Typically used for pitch.
ROW2 (cv) — Row 2 CV output. Outputs the current step's Row 2 knob value. Use for filter, amplitude, or any modulation.
ROW3 (cv) — Row 3 CV output. A third modulation lane. Use for effects, panning, or anything else.
GATE (gate) — Gate output. High when the current step has its gate enabled in the pattern. Length controlled by PW knob.
TRIG (gate) — Trigger output. A short 1ms pulse on each advance to a gate-enabled step. Use to trigger envelopes or sample-and-hold.
CLK (gate) — Clock pass-through. Outputs a gate on every step advance regardless of gate pattern. Useful for chaining sequencers.

Controls

BPM — Internal clock tempo (20-300 BPM). Only active when no external clock is patched to CLK.
Steps — Sequence length, 1 to 8 steps. The sequence loops after this many steps. Modulatable via STEPS CV input.
Run — Start/stop toggle for the internal clock. When stopped, the sequence holds on its current step.
Gates — Gate pattern as an 8-bit number (0-255). Each bit enables/disables the gate for that step. 255 = all gates on, 0 = all off. For example, 237 (binary 11101101) mutes steps 2 and 5.
PW — Pulse width for the gate output (0.1 to 0.9). Higher values = longer gate. 0.5 means the gate is high for half the step duration.
Glide — Portamento between steps (0 to 1). At 0, CV changes instantly. Higher values slide smoothly between pitches for legato melodies.

Inspired by

The lineage runs straight back to the Moog 960 in 1968 and Buchla 245 of the same era — three rows of step knobs, one shared step counter, separate CV and gate outputs. Our take adds modern conveniences (internal clock, glide, per-step gate bitmask, per-step trigger outs) without disturbing the classic architecture.

Doepfer A-155
Moog 960 Sequential Controller
classic 8-step CV/gate sequencer

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