Tools

MIDI In

MIDI-to-CV bridge - turn a hardware keyboard or DAW into V/Oct, gates, and modulation CV.

What is a MIDI In?

A MIDI Input module is a translator. On one side it speaks MIDI - the digital messaging standard ratified in 1983 that lets keyboards, sequencers, drum machines, and computers talk to each other. On the other side it speaks CV/Gate - the continuous control voltages a modular synthesizer eats. Its job is to take incoming MIDI events and convert them into the equivalent voltages: note number becomes V/Oct, note-on/off becomes a gate, velocity, aftertouch, mod wheel, and pitch bend each become their own continuous CV stream.

Before MIDI existed, modular synths had no standard way to talk to anything but themselves. You patched a keyboard's CV out to a VCO's V/Oct input and that was the connection - one voice, one wire, no concept of channels or polyphony. MIDI gave instruments a serial protocol: any number of notes, any number of channels, all carried over a single cable. But MIDI is digital, and a modular synth still wants volts. The MIDI-to-CV converter is the bridge.

Conceptually it works like this: when a Note On arrives, the converter picks the most recent note (last-note priority) and outputs its pitch as a voltage on 1V/Oct (one volt per octave, the modular standard since 1968). It raises a gate line to indicate a key is held; when the key releases and no others are held, the gate falls. Velocity, pressure, mod wheel, pitch bend - each becomes its own CV output, ready to be patched at any modulation destination.

Our MIDI In

Webrack's MIDI In is 8 HP and uses the browser's Web MIDI API to enumerate any USB or Bluetooth MIDI device the OS knows about. Connect a keyboard, a MIDI controller, or route MIDI from a DAW into the browser - the module appears as a CV/gate generator with eight outputs: V/Oct, Gate, Velocity, Aftertouch, Mod, Bend, Retrig, and MIDI Clock.

We are deliberately monophonic with last-note priority. Modulars are voltage machines and one V/Oct line carries one pitch at a time; trying to fake polyphony by stacking voices is a job for a different module (or several MIDI Ins on different channels). What we do well is mono: legato glides smoothly, the gate stays high while you transition between held notes, and the retrigger output lets envelopes re-fire without an artificial gate drop.

Three knobs shape the feel. Channel filters MIDI channel (0 = all, 1-16 = specific) for multi-instrument setups. Bend sets the pitch-bend range in semitones (1-24). Glide adds portamento via a one-pole smoother on the V/Oct output - 0 is instant, 1 slides over roughly 500ms. The classic MS-20 / 303 behavior in three knobs.

In a patch

The canonical MIDI-to-CV patch is the simplest playable modular voice: MIDI In V/OCT -> VCO v-oct, MIDI In GATE -> ADSR gate, ADSR -> VCA cv, VCO audio -> VCA audio in -> Output. Press a key on your keyboard, hear a note. That's the entire chain - everything else is decoration.

Layer in expression: route VEL to the same VCA's CV input through a CV Mix so harder hits play louder; route MOD to an LFO depth or Filter cutoff for performable vibrato or filter sweeps; patch BEND to a second VCO's pitch input so pitch-bend gestures also detune a layer for chorus-style thickness.

Use the CLK output to slave Webrack's sequencers to an external DAW. If your computer is sending MIDI clock alongside notes, each MIDI clock tick becomes a 1ms pulse here - feed it into a Clock Divider to derive quarter notes, eighths, sixteenths, and trigger a Step Sequencer or Euclidean in lockstep with the host.

Outputs

V/OCT (cv) — Pitch CV following the 1V/octave standard. 0V is middle C (C4, MIDI note 60). Each octave up adds 1V, each semitone adds 1/12V. Patch this to any oscillator's V/Oct input.
GATE (gate) — 10V while any key is held down, 0V when all keys are released. This is your primary trigger for envelopes and VCAs. With multiple keys held, the gate stays high until the last key is lifted.
VEL (cv) — Outputs the velocity of the last note-on event, scaled from 0V (lightest touch) to 10V (hardest). The value is held until the next note-on arrives. Route it to filter cutoff or VCA level for expressive dynamics.
AFT (cv) — Channel aftertouch (key pressure). As you press harder on held keys, this rises from 0V toward 10V. Great for adding vibrato depth, filter movement, or volume swells while holding a note.
MOD (cv) — Mod wheel (MIDI CC1) output, 0-10V. The mod wheel is the classic real-time performance control. Route it to LFO depth for vibrato, filter cutoff for timbral sweeps, or any modulation target.
BEND (cv) — Pitch bend output, bipolar. Centered at 0V, swings positive when you push the wheel up and negative when you pull down. The voltage range depends on the Bend knob setting. Route this independently for effects separate from pitch.
RETRIG (gate) — Retrigger pulse. Fires a 1ms 10V pulse each time a new note-on arrives while another note is already held (legato playing). Patch this to an ADSR's retrigger input so envelopes re-fire on each new legato note without the gate dropping to zero.
CLK (gate) — MIDI clock output. If your MIDI controller or DAW sends clock messages (24 pulses per quarter note), each one becomes a 1ms trigger pulse here. Use it to sync Webrack's sequencers and clock dividers to an external tempo source.

Controls

Chan — MIDI channel filter. Set to ALL (0) to receive notes from any channel, or dial in 1-16 to listen to only one specific channel. Useful when multiple MIDI devices are connected or when your controller sends on a specific channel.
Bend — Pitch bend range in semitones. This sets how far the pitch wheel bends the V/Oct output. The standard is 2 semitones (a whole step), but you can go up to 24 (two full octaves) for dramatic pitch sweeps.
Glide — Portamento time. At 0 the pitch jumps instantly between notes. Turning it up adds a smooth glide between pitches - the V/Oct output slides from the old note to the new one. At maximum it takes about 500ms to complete the slide.

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