Midinette

A small Parisian MIDI library: naïve and sentimental about the standard, light on its feet across platforms.

Midinette is a set of F# MIDI tools. It covers messages, sysex, registers and device-specific bits for Elektron and Waldorf gear. A cross-platform port backend is built on midir.

Layout

Path	What
src/midinette	Core: MidiMessage, sysex helpers, midi.ByteStream raw-byte parser, IMidiPlatform / IVirtualMidiPlatform (netstandard2.0;net10.0)
src/midinette.platform.midir	Port backend on midir via a small Rust cdylib (net10.0)
native/midinette-midir-ffi	The Rust C-ABI shim over midir 0.11
src/midinette.elektron, src/midinette.waldorf	Device specifics
samples/MidirMonitor	Lists ports, creates "Midinette In/Out" virtual ports, echoes and prints
tests/*	Expecto test projects, run with dotnet test

Midir backend

open midi
open midinette.platform
open midinette.platform.midir

let midi = MidirPlatform("my app")              // client name shown by the OS
for p in midi.InputPorts do printfn "%s" p.Name // re-enumerated on each access (hot-plug)

// open a hardware port by name
match midi.TryFindOutput "Elektron MachineDrum" with
| Some port ->
    use out = midi.GetOutput port
    out.Open()
    out.WriteMessage(MidiMessage.Encode 0x90uy 60uy 100uy)
    out.WriteSysex [| 0xF0uy; 0x7Euy; 0x7Fuy; 0x06uy; 0x01uy; 0xF7uy |] // identity request
| None -> ()

// virtual ports (macOS CoreMIDI, Linux ALSA; not Windows)
if midi.SupportsVirtualPorts then
    use vin = midi.CreateVirtualInput "Midinette In"   // already open
    let input = vin :> IMidiInput<int64>
    use _ = input.ChannelMessageReceived.Subscribe(fun e -> printfn "%O" e.Message)
    use _ = input.SysexReceived.Subscribe(fun s -> printfn "sysex %d bytes" (UMX.untag_sysex s).Length)
    ()

Behaviour:

• Events are raised on a per-input dispatcher thread, never on midir's thread. Once Close() / Dispose() returns, no more events are raised.
• Sysex comes in reassembled (up to 16 MiB by default). Realtime bytes interleaved in a sysex are delivered separately. Running status is expanded.
• Close / Dispose are idempotent. Opening a port that disappeared raises MidirException.
• On macOS the shim reframes output for CoreMIDI so the loopback is lossless:
  • sysex of 64 KB or more goes out in 16 KB packets, because CoreMIDI packets top out at 65535 bytes;
  • every sysex gets its own packet, because midir's CoreMIDI input would treat bytes after it in the same packet as sysex;
  • running status is expanded, because midir's CoreMIDI input drops running-status data bytes;
  • realtime bytes interleaved in a sysex are sent just before it, because CoreMIDI truncates the sysex at them. Input from other apps or drivers is taken as CoreMIDI hands it over, and the same midir limits apply to it.
• Input close never races the OS callback: the shim gates the managed callback and drops the connection instead of using midir's close(), which can panic on CoreMIDI.
• IMidiOutput timestamps are ignored: messages are sent immediately.
• Virtual ports: SupportsVirtualPorts is true on macOS and Linux/ALSA. On Windows it is false and CreateVirtual* throws PlatformNotSupportedException. Use loopMIDI or Windows MIDI Services loopback endpoints there.

Build and test

Requirements: the .NET 10 SDK and a Rust toolchain (cargo). Linux also needs libasound2-dev.

dotnet test midinette.slnx                    # builds the Rust shim via cargo, then runs every Expecto project
dotnet run --project samples/MidirMonitor -- --seconds 30

• The Midir project runs cargo build --release on native/midinette-midir-ffi before building, then copies the native library next to the assembly.
• To use a prebuilt shim, pass -p:MidinetteSkipCargo=true and drop libmidinette_midir.{dylib,so} / midinette_midir.dll into native/midinette-midir-ffi/target/release/.
• Virtual-port tests (loopback in both directions over every channel voice, system common and realtime message, sysex from 2 B to 64 KB+1, running status, seeded fuzz, a 70k-message flood that checks for loss, order and timestamps, garbage-stream recovery, close-while-flooding, 1000× open/close soak) only run where virtual ports work: macOS, and Linux with /dev/snd/seq. Elsewhere they are skipped.
• Test projects are plain executables too: dotnet run --project tests/midinette.platform.midir.tests -- --summary.

Packages are managed centrally in Directory.Packages.props. Paket and FAKE are gone.

Legacy

src/midinette.platform.rtmidi, src/midinette.platform.portmidi and src/midinette.fable are kept for reference but are no longer in midinette.slnx or maintained. They still reference the old paket setup. New code should use midinette.platform.midir. midir is the path to drop them once its coverage is proven on real hardware.