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If I have multiple note-on MIDI messages occurring at the same time (simultaneously as a chord) should I be concerned about the velocity applied to each note-on to avoid things like clipping and other disturbing results? For example: I have 4 note-ons and each of them has a velocity of e.g. 100, what will the final sum of velocities be? The velocity data byte has only 7 bits, so 400 can't be represented there. Does this lead to damaged midi data at the end? Should I calculate the desired velocity for a chord by assigning each note its own portion, i.e. 100/4?

2 Answers 2

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There are several misconceptions here…

  1. That a chord needs to 'share' the velocity information.
    It doesn't. Each Midi Note On carries its own separate velocity parameter. This means you can have as many notes as you like on simultaneously [up to the poly count & subject to data transmission speeds] & each can have its own velocity.
    You can't 'damage the midi data' in this way.

  2. That you can add volumes based on velocity.
    Of course, the more simultaneous notes, the louder the sound is likely to be, but this is entirely within the 'sound' [analog or digital equivalent] domain, not strictly related to the midi data. When the playback device was first voiced, someone would have made sure there is headroom in the signal path so distortion doesn't occur. It's then up to you in your mix console/USB interface that you gain stage correctly for input/output levels. Not all midi voices gain actual loudness as the velocity increases. Some may just change a filter, or attack parameter etc.

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You're mixing MIDI and audio in your question. But MIDI is not audio. MIDI is just about instructions for synth. MIDI velocity means nothing until a note will be rendered to audio via a synth or DAW. We're not able to predict how multiple velocities will be combined in the synth. Maybe the synth has a logic to prevent clipping and so on.

Velocity 100 means just we've attached a number (which usually correlate with volume in result audio, but that's not always true) to a note. So in general case we can't say what volume in dB a note will have after its velocity is rendered by a specific synth. One synth can render it to -10 dB (in terms of digital audio), while second one to -5 dB.

My recommendation is to assign each note of a chord the same velocity which we will consider as the velocity of the whole chord.

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