Re: Midi Volume Control
Re: Midi Volume Control
- Subject: Re: Midi Volume Control
- From: "James Chandler Jr" <email@hidden>
- Date: Tue, 25 Jan 2005 18:56:46 -0500
Perhaps one would maintain the first VolumePedal CC7 on each track, as the
'initial' volume setting of the track, and then convert any subsequent CC7's to
Expression CC11 (if additional CC7's exist)? Many sequencers will save 'tracks
window' track volume settings to the beginning of a MIDI file, so that is why
the first-encountered CC7's should probably be preserved.
Many folks actually use Expression rather than VolumePedal for the right thing
nowadays, so a 'properly made' MIDI file would only have a single CC7 per track,
and the MIDI Player's converter process wouldn't make anything bad happen.
If there is a 'GM Reset', 'GS Reset', 'XG Reset' or other such reset message in
the MIDI file, perhaps the messages should be detected, and interpreted as a
command for the player program to initialize all its CC7 tracking globals to
nominal? Isn't the nominal Volume value 100 for Reset messages? Can't recall at
the moment.
Here is a question perhaps Tom or someone else will know--
Many moons ago, I experimented mapping velocity and volume to the actual audio
volume coming from a synthesizer. Wanted to optionally mark MIDI Mixer window
volume sliders in dB, and also automate "master fadeout" type functions, fading
MIDI and audio with the same amplitude scalings.
Tested a bunch of synths. The audio amplitude correspondence to CC7 value was
all over the map. Each manufacturer seemed to have a different idea of how CC7
values should map to audio gain. There were even differences between different
synth models from the same company. I may be remembering wrong, but for instance
the Yamaha TX81 didn't even have the same CC7 volume curve as the Yamaha DX-7.
Not picking on Yamaha here, most companies had the same issue.
Is there a recent MMA spec on how CC7 should affect the audio amplitude response
curve? Do modern synths have more consistent CC7 amplitude response curves than
in the dim past?
I only mention the amplitude curves in the context of scaling CC7's to control
master volume. Even if the MIDI file is driving a single multi-timbral synth, if
you don't know the CC7 amplitude curve of the synth, there seems no way to
reliably control the master volume and also keep the intended instrument mix.
For instance, if you subtract 5 from all the tracks' CC7 values, there is no
guarantee that this will attenuate all tracks the same value in dB? That was at
least the situation in the old synths I tested.
Thanks
JCJR
----- Original Message -----
From: "Tom White" <email@hidden>
To: "'CoreAudio List'" <email@hidden>
Sent: Tuesday, January 25, 2005 6:14 PM
Subject: RE: Midi Volume Control
For the fallback, I think I'd scan the sequence and replace all CC7 events
by
CC11 events, recalculating the volume setting for the new CC11 as
necessary.
You won't always need to recalculate the CC11 volume setting, just in
those
situations where both types of event occur on the same channel. Once
you've
done this, you've freed up CC7 to control the volume of each channel.
This is an interesting suggestion.
Though its a little strange to do this to a file post-creation, it does
comply with
the GM recommendation which states that CC11 is for crescendo/decrescendo
during performance, while CC7 is for relative instrument balance (like a
mixing
console).
- Tom White
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