What MIDI is

  • Musical Instrument Digital Interface
  • Proposed in 1981, announced in 1982, first public demo in January 1983
  • Transmits performance data, not audio

What MIDI sends

  • Channel voice messages: note on/off with velocity, poly key pressure, channel pressure, control change, program change, pitch bend
  • Common controller (CC) mappings: CC1 modulation, CC7 volume, CC10 pan, CC11 expression, CC64 sustain
  • System messages: clock, start/stop/continue, time code, machine control

Sync options

  • MIDI Clock for tempo/beat sync (24 pulses per quarter note)
  • MIDI Time Code for absolute time in hours:minutes:seconds:frames
  • MIDI Machine Control for transport commands

How Midi Connects: Physical Layers

  • 5-pin DIN current-loop at 31.25 kbaud (legacy, still common)
  • USB-MIDI for computers, tablets, phones
  • 3.5 mm TRS MIDI (Type A/B) standardized in 2018
  • Bluetooth LE MIDI for wireless setups
  • RTP-MIDI over Ethernet/Wi-Fi (built into macOS/iOS; Windows driver available)
5-pin DIN connector
5‑pin DIN connector
TRS MIDI connector
3.5 mm TRS MIDI connector

MIDI device types

  • Controllers send data only
  • Sound modules receive MIDI and generate audio
  • Workstations and grooveboxes integrate controller, sounds, sequencer
  • Alternate controllers (NIMEs) explore new performance paradigms

Case study: a classic rack module

  • Roland Fantom-XR (mid-2000s)
  • 128-voice polyphony, ROMpler + sampler, SRX expansion slots
  • Controlled entirely via MIDI
Roland Fantom-XR
Roland Fantom‑XR module

Case study: workstations and grooveboxes

  • Akai MPC lineage (from MPC60 in 1988)
  • Sampling + sequencing + pads in one box
  • Timing correct, note repeat, and swing as defining workflow concepts

Alternate controllers (NIMEs)

  • New Interfaces for Musical Expression
  • Examples: MPE surfaces (ROLI, LinnStrument), multitouch, gestural/VR, hex guitars

MPE: per-note expression

  • Each note gets its own channel within a zone
  • Per-note pitch, timbre (often CC74), and pressure
  • Adopted in 2018; v1.1 updates in 2022
  • Supported by major DAWs and many instruments

MIDI 2.0 overview

  • MIDI-CI for capability discovery and negotiation
  • Higher-resolution control, per-note articulation in the new protocol
  • Universal MIDI Packet format (32–128-bit), groups × channels
  • Designed for high-speed transports like USB and network MIDI
  • Backward compatibility pathways to MIDI 1.0

Practical lab

  • in Reaper, add a MIDI clip with multiple notes
  • Draw in pitch bend and velocity changes that affect all notes (channel-wide)
  • Listen to how they affect the sound differently