Sequencing & Clock

SEQ4

A four-step CV/gate sequencer - patch a clock in, get a melody out.

What is a SEQ4?

SEQ4 is the smallest sequencer in the rack: four step knobs, a clock input, a reset input, a CV output, and a gate output. Each rising edge on CLK advances the sequencer one step; the four-step cycle wraps and starts over. No internal clock - SEQ4 stays silent until you patch one in. The first sequencer in the Basic series, designed to teach the concept of a sequence with as little surface area as possible. When you outgrow it, SEQ8 adds three rows, eight steps, an internal clock, glide, and per-step gate toggles. But SEQ4 is enough to make a melody, and that is the lesson.

In a patch

The teaching patch: Clock CLK -> SEQ4 CLK; SEQ4 CV -> VCO V/Oct (one octave across the 0-1V range); SEQ4 GATE -> Basic AD GATE; AD ENV -> VCA CV; VCO -> VCA -> Output. With the default step values [0V, 0.25V, 0.5V, 0.75V] you get a four-note ascending arpeggio at the clock rate - patch and listen. Twist each step knob to change the melody. Patch a button or a slow LFO into RST to restart the phrase. For a stricter scale, run CV through Quantizer before V/Oct - the 0-1V range covers any 12-tone scale across one octave. The LED row at the top shows which step is currently playing, so you can hear AND see the sequence advancing.

Inputs

CLK (gate) — Clock input. Rising edges (signal crosses 2.0V going up) advance the sequencer one step. Eurorack-standard 0-10V gate threshold. The gate output mirrors the clock signal's high time, so a square clock produces square gates and a narrow trigger pulse produces narrow gate pulses. SEQ4 has no internal clock - until you patch a clock in here, the sequencer stays at idle (CV=0V, GATE=0V).
RST (gate) — Reset input. A rising edge here jumps the sequence back to "before step 1," so the next clock edge plays step 1. There is a 1ms lockout after reset - clocks within that window are absorbed, which prevents a simultaneous CLK+RST edge from being mis-counted as advancing past step 1. Patch a Basic Button into RST to manually restart phrases, or a longer-period clock divider for compound sequences.

Outputs

CV (cv) — Sequenced CV output. 0-1V, the value of the currently-playing step's knob (clamped). At V/Oct (1V per octave) this spans exactly one octave - 12 semitones - so step value 0.0 = root, 0.083 = +1 semitone, 0.5 = +6 semitones (a tritone), 1.0 = +1 octave. Patch into a VCO V/Oct input for melody, or into a filter cutoff CV for stepped tonal changes. For tighter tuning patch through Quantizer.
GATE (gate) — Gate output. 10V while the input clock is high (after the first clock arrives), 0V otherwise. The pulse width is whatever the input clock produces - usually 50% from a Clock module, narrower if you patch a trigger source. Patch into Basic AD's GATE input to shape each step as a pluck, or into a VCA CV input to gate the audio path on/off per step.

Controls

Step 1 — Voltage for step 1. Range 0-1V, linear scale. Default 0V (root note when patched into V/Oct). Twist clockwise to raise pitch by up to one octave. At 1/12 increments (about every 8% of knob travel) the pitch lands on a chromatic semitone; for in-tune notes patch through Quantizer.
Step 2 — Voltage for step 2. Range 0-1V. Default 0.25V = +3 semitones from 0V (a minor third up - the second note of an arpeggio).
Step 3 — Voltage for step 3. Range 0-1V. Default 0.5V = +6 semitones (a tritone, halfway across the octave).
Step 4 — Voltage for step 4. Range 0-1V. Default 0.75V = +9 semitones (a major sixth - the highest note in the default arpeggio before wrapping back to step 1).

Inspired by

Four step knobs, one shared step counter, separate CV and gate outputs. The smallest CV/gate sequencer that can teach what a sequence actually is. When the learner outgrows it, SEQ8 adds three rows, eight steps, an internal clock, glide, and a per-step gate pattern.

Korg SQ-1 (4-step mode)
Doepfer A-155

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