Sequencing & clocks

No single transport governs every module in vxsynth. The studio carries tempo as a signal on a cable: a clock is a module that sends out short, steady voltage pulses, and you patch a clock into other modules to make them play in time. Free-running clocks like BPM Clock each keep their own tempo. The automation timeline has a tempo of its own, set in the dock's BPM field. Two things can put a module in step with it: set the module's Clock control to Song, or patch Song Clock into its CLK input.

How playback works

The power button in the top bar turns the audio engine on and off. It does not start a song. Turning it on un-mutes the whole engine.

Once audio is on, the engine runs continuously. Every clocked module advances one step each time a pulse arrives at its CLK (clock) input. The studio's default step is a 16th note.

The simplest working setup is one cable. Patch BPM Clock, with Div set to 1/16, into your sequencer's CLK input. A sequencer makes no sound until it receives clock pulses.

To stop and start a patch by hand, clock it from the Song Clock module instead of a free-running clock. Song Clock's pulses come from the automation timeline, and its play and stop buttons halt the timeline, which freezes everything it clocks. Modules set to Song follow the timeline directly and stop with it, without a cable.

The Automation dock plays separately

The Automation dock at the bottom of the screen has its own play and stop buttons. On their own, they move only the automation lanes. Two things make that transport drive your sequencers as well: set a sequencer's Clock control to Song, or patch Song Clock into its CLK input, which turns the timeline's beat counter into clock pulses. Song suits the seven sequencers that offer it, because they then follow scrubs and loops exactly. Song Clock suits everything else, and it is the only option for modules without a Clock control. See Automation.

The clock modules

These modules generate and shape clock pulses.

  • BPM Clock is the master clock. Set the tempo from 20 to 300 BPM (beats per minute) and a Div from 1/1 (one pulse per bar) down to 1/32. Its CLK output sends a clean 10 ms pulse that drives any clocked module.
  • Clock Divider and Clock Mult make slower and faster rates from one master clock. The Clock Divider passes every Nth pulse, where N runs from 1 to 256. The Clock Mult measures the gap between two pulses and fills it with 1 to 16 evenly spaced pulses, so it keeps up with tempo changes.
  • After counts pulses and turns a gate on when the count reaches its COUNT setting, which ranges from 1 to 512. A gate is a voltage that stays on to mean "play" and off to mean "stop". Set COUNT to 64 and After's GATE turns on after 64 pulses, then stays on. Chain several After modules through their HOLD inputs to trigger sections of an arrangement in sequence.
  • Patch Start fires a single pulse the first time a patch makes sound after loading. Wire it into RST inputs so the patch always starts from the beginning.
  • Song Clock is the automation timeline's clock and transport as a module. Its CLK output pulses in step with the timeline's beat counter, so sequencers it drives stay locked to your automation curves. Its play, stop, and reset buttons control the song, and its START, STOP, and RST inputs do the same from a cable, so another module can stop the patch for you.
  • MIDI-CV converts an incoming MIDI clock (24 pulses per quarter note) into a CLK output and a divided CLK·N output. It also sends START and STOP pulses that mark when a DAW (music recording software) starts and stops playback.

Any voltage that rises above about 1 V counts as a pulse. An LFO (a slow modulation source) set to a square wave can therefore clock a sequencer as well as a dedicated clock module can.

Modules that step

The Sequencers category turns clock pulses into notes and rhythms.

  • The Piano Roll is a note editor. Enter notes for four tracks on one grid. Each track has its own V/OCT and GATE output, where V/OCT is a pitch signal at one volt per octave and GATE marks when that track's note plays.
  • Step Seq is a step sequencer that outputs a control voltage (CV), a voltage that stands in for a knob setting. Paint a value into each column, then clock it to play a melody, a bassline, or rhythmic modulation.
  • Drum Seq and Prob Seq are 8-lane pulse grids. Each lane fires a pulse on its own output when its active steps come round. Prob Seq gives each step a probability, so a lane can fire at random odds you set.
  • Euclid Seq spreads a chosen number of hits as evenly as possible around a loop.
  • Weaver builds a changing melody from six layered voltage shapes.

Two Devices contain a sequencer of their own: the VX-303 acid machine and the VX Cells grid instrument.

Choosing a clock

Seven sequencers have a Clock control with three settings. The Piano Roll, Step Seq, Drum Seq, Prob Seq, Weaver, VX-303, and VX Cells all work this way.

  • Ext is the default. The cable patched into CLK drives the sequence, one pulse per step.
  • Int runs the module at its own tempo. Enter a value in the BPM box and press Run. No clock cable is needed.
  • Song ties the module to the automation timeline. It plays one step per sixteenth note, counted from the start of the song, so rewinds, scrubs, and loops in the Automation dock move it immediately.

In Song mode a module works out its position from where the playhead is, rather than counting the pulses it has received. Move the playhead to bar 33 and you hear what belongs at bar 33, the same every time you go back to it. This is what makes these modules usable in an arrangement: the song plays back the same way twice.

The BPM box is editable only in Int, because that is the only setting where the module's own tempo is in use. In Ext the cable sets the pace, and in Song the timeline does, so the box dims. In Song it shows the song's tempo.

The Run and Stop buttons work only in Int, for the same reason. The Rewind button works in every setting: in Ext and Int it restarts the module, and in Song it rewinds the whole song.

Every other clocked module runs from an external clock only.

Resetting to the start

Nearly every clocked module has an RST (reset) input. A pulse into RST sends the module back to the beginning, so its next pulse plays step 1.

BPM Clock passes an incoming reset through to its own RST output, re-shaped into a full pulse, so several modules can share one reset from a single source.

Two setups cover most needs:

  • Patch Patch Start into every RST input so the whole patch starts aligned when it loads.
  • Send a bar-rate pulse into the reset inputs at the top of a phrase to pull drifting parts back into time.

Tips

  • Start with two modules. Patch BPM Clock (Div 1/16) into Drum Seq's Clk, then send the same CLK to everything else. One tempo knob then controls the whole patch.
  • Run a melody at half speed under fast drums. Patch BPM Clock's CLK into Clock Divider (Ratio 2), then into Step Seq's Clk. The timing relationship holds as you change tempo.
  • Build an arrangement with After. Set COUNT to 64 and patch its GATE into the CV input of a VCA (a level control driven by voltage) on a second layer. With a 16th-note clock, that layer enters after four bars.
  • Thin out a busy hi-hat line. Route the clock through Prob Gate on the way to the hi-hat, so Prob Gate passes or drops each pulse at random.
  • Sequence from a DAW. Patch MIDI-CV's CLK·N output (set to 1/16) into a sequencer's CLK, and its START output into RST. The rack then follows your DAW's play and stop.