MIDI2 Monitor MK2

MIDI2 Monitor MK2 is a macOS app for anyone building, testing, or debugging MIDI 1.0 and MIDI 2.0 devices and software. It captures live MIDI traffic via CoreMIDI and decodes every UMP message — including MIDI-CI Profile-specific data like Note Attribute types and Flex Data (tempo, time signature, chord name, metadata) — into clear, readable detail down to the individual bit field. What sets it apart is its accessibility-first design: an extensive text-to-speech system narrates messages aloud per device, with adjustable rate, volume, and voice, plus a spoken “catch-up” review and audible message ticks — making it possible to monitor MIDI activity without watching the screen at all. Filtering, CSV export, and a configurable message buffer round out the toolset for serious MIDI development work.

1. MIDI2 Monitor MK2’s innovation around MIDI 2.0 goes past raw bytes to decode spec-level detail few tools touch — MIDI-CI Profile Note Attribute data (Orchestral Articulation, Drums) and Flex Data content like tempo, time signature, and chord name, down to individual bit fields. 2. On text-to-speech, it narrates every message in plain English per device, making MIDI monitoring accessible to blind and low-vision users, who can follow traffic by ear instead of relying on the screen.

The raw data information, with bit/byte level descriotoins, is useful to engineers and device designers.

But the most inspiring use will probably be by blind musicians, technicians, or developers, being able to build, test, and troubleshoot their own MIDI 2.0 hardware or software entirely independently — something that’s traditionally been closed off to them, since MIDI monitoring tools have always been visual: scrolling hex dumps and message lists on a screen. With this app, someone who can’t see the screen can plug in a device they’re building, hear exactly what it’s sending out — down to individual bit fields and attribute data — and debug it by ear in real time, with no sighted assistant needed to read the screen for them.

That’s a meaningful shift for a technical field: it turns a niche diagnostic tool into something that opens MIDI development itself up to people who’d otherwise be locked out of the tooling, not just the music.