# What do public sources state about MIDI 2.0 (UMP, MIDI-CI) interchange with MIDI 1.0, and what does one open implementation lose when converting MIDI 2.0 messages down?

- id: art_01M5NP4VY04795QG6PCP8GPHV2
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T14, T16 · tags: none
- updated: 2026-10-24T00:49:35.673Z
- url: https://veyrul.com/articles/art_01M5NP4VY04795QG6PCP8GPHV2

Linux's ALSA sequencer converts MIDI 2.0 to MIDI 1.0 by right-shift truncation (32-to-7 bits >>25, 32-to-14 >>18, 16-to-7 >>9). A bank-valid program change becomes bank-select controller messages followed by a program change. Only note on/off, poly pressure, control change, program change, channel pressure and pitch bend are converted; other MIDI 2.0 channel-voice statuses are dropped. Upscaling uses a bit-repeat scheme. This is one implementation's behaviour, read from code.

Linux's ALSA sequencer converts MIDI 2.0 to MIDI 1.0 by right-shift truncation (32-to-7 bits >>25, 32-to-14 >>18, 16-to-7 >>9). A bank-valid program change becomes bank-select controller messages followed by a program change. Only note on/off, poly pressure, control change, program change, channel pressure and pitch bend are converted; other MIDI 2.0 channel-voice statuses are dropped. Upscaling uses a bit-repeat scheme. This is one implementation's behaviour, read from code.

Curator qualifications: Kernel code read 2026-10-22; nothing compiled or run (arithmetic only). midi.org page statements carried from producer reading.

Limitations: Kernel code read 2026-10-22; nothing compiled or run (arithmetic only).

Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

```json
{
  "citations": [
    {
      "url": "https://midi.org/midi-2-0",
      "note": "linux sound/core/seq/seq_ump_convert.c at a804c57 L17-41, L432-500; Documentation/sound/designs/midi-2.0.rst at a804c57, General"
    },
    {
      "url": "https://midi.org/spec-detail/",
      "note": "linux sound/core/seq/seq_ump_convert.c at a804c57 L17-41, L432-500; Documentation/sound/designs/midi-2.0.rst at a804c57, General"
    },
    {
      "url": "https://github.com/torvalds/linux/blob/a804c5742bff224d4cb4d25dd383554d598be32b/Documentation/sound/designs/midi-2.0.rst",
      "note": "linux sound/core/seq/seq_ump_convert.c at a804c57 L17-41, L432-500; Documentation/sound/designs/midi-2.0.rst at a804c57, General"
    },
    {
      "url": "https://github.com/torvalds/linux/blob/a804c5742bff224d4cb4d25dd383554d598be32b/sound/core/seq/seq_ump_convert.c",
      "note": "linux sound/core/seq/seq_ump_convert.c at a804c57 L17-41, L432-500; Documentation/sound/designs/midi-2.0.rst at a804c57, General"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] Linux's ALSA sequencer converts MIDI 2.0 to MIDI 1.0 by right-shift truncation (32-to-7 bits >>25, 32-to-14 >>18, 16-to-7 >>9). A bank-valid program change becomes bank-select controller messages followed by a program change. Only note on/off, poly pressure, control change, program change, channel pressure and pitch bend are converted; other MIDI 2.0 channel-voice statuses are dropped. Upscaling uses a bit-repeat scheme. This is one implementation's behaviour, read from code. · locator: linux sound/core/seq/seq_ump_convert.c at a804c57 L17-41, L432-500; Documentation/sound/designs/midi-2.0.rst at a804c57, General · source: https://midi.org/midi-2-0

Rights:
- documentation: license=unknown hosting=permitted redistribution=permitted modification=unknown training=unknown · Applies to this original summary only, not to the cited sources.

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