mpe

MPE

Use this skill when adding per-note expression (pitch bend, pressure, CC 74 timbre) to a Pulp synth, or when writing a host that needs to dispatch MPE data into a plugin. Pulp keeps MPE as an opt-in sidecar to the normal MIDI path — plugins that don't set supports_mpe never see the extra buffer.

When to reach for MPE

• The synth is meant for Roli Seaboard / LinnStrument / Sensel Morph / KMI / similar per-note controllers.
• You need polyphonic per-note pitch bend (not just a global bend).
• You want pressure or CC 74 to modulate each voice independently.

If you only need monophonic aftertouch or a global mod wheel, plain MidiBuffer in process() is simpler — do not reach for MPE.

Decision tree

You're writing...	Use
An MPE synth voice	Subclass midi::MpeSynthVoice, render your oscillator using state().pitch_bend_semitones, state().pressure, state().timbre
An MPE synth plugin	MpeVoiceAllocator<YourVoice> inside the processor, dispatch MpeBuffer in process(), set supports_mpe = true or node_capabilities.supports_mpe = true in the descriptor
A host that loads MPE plugins	Build an MpeBuffer from inbound MIDI (zone-aware) and hand it to Processor::mpe_input() — the CLAP, VST3, and AUv3 adapters already do this
Pure MIDI 2.0 UMP work	Out of scope — direct UMP-native MPE transport is deferred

The three-step pattern for a new MPE synth

1. Scaffold with --mpe

./build/pulp create MySynth --type instrument --mpe

The CLI post-processes the generated descriptor to add .supports_mpe = true or .node_capabilities.supports_mpe = true and includes <pulp/midi/mpe_buffer.hpp>. No manual wiring required.

2. Declare the voice

class Voice : public pulp::midi::MpeSynthVoice {
public:
    void on_note_on(const pulp::midi::MpeNoteState& n) override {
        pulp::midi::MpeSynthVoice::on_note_on(n);  // keep base bookkeeping
        // your per-voice init
    }
    void render(float* out, int n) override {
        const auto& s = state();       // read the tracked expressions
        // s.pitch_bend_semitones, s.pressure (0..1), s.timbre (0..1)
    }
};