Duo MIDI

A duophonic MIDI-to-CV + envelope card! The first ever card released using Blackbird as a platform under the hood.

Customize the behavior to make your own midi card by opening the duo_midi.lua file in web-druid. Note this script is big so you need to use the upload button in web-druid. for some reason run doesn't.

The version of blackbird included in the UF2 (version 1.1M) is technically unreleased at the time of writing because I haven't tested much blackbird functionality other than this script (so if you load a different script onto it, YMMV).

What it does

• Receives MIDI note, velocity, pitch bend, and mod-wheel (receives on all channels)
• DUO mode: Does round-robin style voice allocation (voices are distributed regardless of MIDI channel)
• MONO mode: Outputs incoming midi to both voices
• Outputs two pitches (duophonic or mirrored mono).
• Outputs two ASR envelopes (at the audio outputs).
• Outputs two triggers / gates on voice assignment.

Controls

Switch

• Up: Duophonic (two voices, dynamically assigned).
• Middle: Monophonic (both channels mirror the same note).
• Down: Toggles gate mode for pulse outputs.
  • Gate mode off (default): pulse outputs emit a 10ms trigger on voice assignment.
  • Gate mode on: pulse outputs behave like gates (high while the voice is active).

Note: Device/Host mode switching is automatic, but changing it requires a Workshop Computer power cycle.

Knobs

• Main: Velocity sensitivity (scales envelope level by MIDI velocity).
• X: Envelope attack.
• Y: Envelope release.

MIDI behavior

• Pitch bend: ±2 semitones (configurable in code via BEND_RANGE).
• Mod wheel (CC #1): Sets pitch slew on outputs 1–2 from 0 to 1 second.

Voice allocation (duophonic)

When two voices are active, new notes get assigned to the closest existing voice (by pitch distance). When only one voice is active, notes within ~5 semitones tend to reuse the nearby voice; otherwise they take the other voice.