rearrange-test.text
Chris Ahlstrom
2025-07-03

https://midi.org/community/midi-specifications/reordering-simultaneous-events

    Reordering of events can be problematic. It is not recommended.

    Your specific example of a Note Off and a Note One can cause a problem,
    although not in all cases. Sometimes a synthesizer will use this order in a
    meaningful way. For example, in Mono Mode, many synthesizers will perform a
    legato transition if they receive a new Note On before receiving a Note Off
    for the previous note. Another example would be a sophisticated piano, such
    as those that use 3 key sensors, which might use that same order to
    signify when a key is returned only half way up then restruck such that
    the damper does not touch the string between hammer strikes. In either
    of those examples, switching the order of events changes the response
    of the receiver.

    https://rnhart.net/midi/attachments/re-arrange-test.zip

    By the way, I just did some tests by connecting MIDI player software I have
    on my computer to MIDI monitor software MIDI-OX using a virtual MIDI cable
    loopMIDI, then checking the message order shown in the MIDI-OX monitor
    window. It looks like about half of the MIDI players I have move note ends
    before note starts if they happen at the same time position in the MIDI
    file. So some other MIDI software developers have also considered this a
    good idea.

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