Re: dynamic and midi velocity

[David Raleigh Arnold]

On Thursday 04 March 2010 18:36:01 Philippe Hezaine wrote:
> Martin Tarenskeen a écrit :
> > On Thu, 4 Mar 2010, David Raleigh Arnold wrote:
> >> So why on earth is conversion from velocity to volume in decibels an
> >> issue?  If you are using ppp pp p mp mf f ff fff why convert at all?
> >> Just use velocity.  Regards, daveA
> >
> > That was not the issue being discussed here.
> >
> > When we are talking about "Velocity" and "Volume" we are talking - at
> > least in this thread - about two different specific MIDI messages.
> >
> > Velocity is a 7 bit value (0~127) that is part of a MIDI Note-On or MIDI
> > Note-Off message. Each single note has such a value in a MIDI stream.
> >
> > Volume is one of the MIDI Control Change messages, Nr. 7 to be exactly.
> > These can not be specified for each single note, but for each of the 16
> > MIDI channels.
> >
> > Velocity and Volume are used for different purposes in MIDI sequencers
> > and MIDI files.
> >
> > Currently if Lilypond scores are exported as MIDI files, the ppp mf ff
> > and so on are written as MIDI Volume values, not as MIDI Velocity values.
> >
> > In many cases MIDI Velocity messages are more suitable to translate such
> > dynamics into MIDI. That's why people are interested in that conversion
> > script. (including me)
> 
> Here are excerpts of discussions with Dominic Sacré when I used
> mididings instead of midicomp.
> 
> "The problem you're probably noticing here is that CC7 (and all other
> controllers) always pertain to a whole MIDI channel. The only way to
> have two notes at the same time on the same channel, but with different
> volumes, is to use the note-on velocities (as you know)."
> 
> 
> "The volume controller doesn't interact with individual notes at all. It
> just changes the volume immediately, affecting all notes on the
> respective channel, even those which are already playing at that time."
> 
> 
> "... all tracks in your MIDI file are on the same channel, so CC #7
> messages on one track will affect the other tracks as well."
> 
> Hope this helps to understand some differences between CC7 (volume) and
> velocities.
> Cheers.
> 

It couldn't be simpler.

Ideally the volume should be preset for each instrument according to
ratios expressing the relative natural loudness of the instrument, IOW
set it and forget it, and only velocity should be used for dynamics.  That is 
obviously the purpose of the design.  Why fight it?  No good can come from 
twiddling the volume in the middle of the performance.  Regards, daveA

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