[music-dsp] Polyphony - how do you mix N number of signals and keep a consistent volume?
rbj at audioimagination.com
Mon Oct 25 14:32:30 EDT 2010
On Oct 25, 2010, at 11:03 AM, Tom O'Hara wrote:
> Actually, it's Log2(n) * -3dB, which is the same as dividing by
Tom's right. David R is right (except for the (N-1)*(-3 dB)). Dave H
is right. Didier is right.
and, in my opinion, Johannes is also right.
i would think that a useful *option* for an organ or sampler (not a B3
simulation, that's a different animal) with potentially 128 note
polyphony, that if the musicians were to lay both his entire forearms
down on the keyboard, that maybe there should be something other than
the volume pedal to limit the volume. for an internal compressor/
limiter, perhaps level detection wouldn't be needed as it would be for
an outboard unit because the compressor/limiter would know the number
of keys pressed.
if the number of keys pressed is N, i might suggest a linear scaling
factor of 1 when N < M, where M is some preset number where this
scaling would begin to kick in. for N > M, perhaps it the linear
scaling factor should be sqrt(M/N), but perhaps some other heuristic
should be considered. this gain signal should always have some kinda
LPF applied to it so that it slews or ramps from one value to the
other reasonably slowly.
but there should always be the volume pedal, in case the scaling
applied by the compressor is not what the musician wants.
i am not sure, but i think a B3 simulation would be applying some
kinda overall scaling based on the number of keys pressed, but i don't
know what it is.
r b-j rbj at audioimagination.com
"Imagination is more important than knowledge."
More information about the music-dsp