ChordWizard Software wrote:
Hi all,
I'm wondering if someone can point me to some good background articles that
illuminate what is happening
to the signal with common effects such as reverb, chorus, flanger, etc.
...
Any pointers much appreciated.
Hello Stephen,
It's a long history that you're asking about, but there are some very
clear points not to hard to distinguish for the technically/science
inclined, without the need for a prior electrical engineering IQ test.
It is required to take a bit of an intelligent approach to the whole
area of effects for musical instruments, unless you want it really
basic, or are only interested in a few main lines.
The primary use of effects in the modern history of music, in the sense
of enhancing a musical instrument, is mostly to make the sound richer.
Be it by adding exciting phasing sounds to an electric guitar, a Leslie
box on Chorus or Vibrato speed to an electric organ, or a artificial
reverberation component to a dry keyboard, being played with headphones.
Of course, as you've noted, there's signal distorting effects (fuzz box,
tube distortion, heavy metal distortion, octavers), delay-based effects
(single/multi-delay, echo, reverb, gated reverb, ambiance, feedback
killer), and there are filtering-based effects (wah wah, equalizer, cry
baby, bass boost, contour/loudness), and more complicated modulated and
signal analyzing effects (warped delay, space warble, computer voice,
grunt voice), and even signal-combining effects like vocoders and
complicated instrument mixing effects. Most of these
effects can be Googled easily.
Presumably you'd want to work only in the digital domain (i.e. no use of
analog electronics for the effects) without inventing software
(machinery ?) with extreme sample rates, or scientifically advanced
signal descriptions (I suppose straight samples at say CD quality or
something of the kind).
That means that the effects you want to create or use (possibly from
legally applied Open Source licenses) are going to have serious
degradation effects coming from the use of sampling. It's almost
certain if you search for pro-grade sampled signal based effects, that
the pro-grade comes from thorough understanding and working around the
sampling issues in the particular effect, as well as from a proper
analysis of the effect you search after. Essentially, that is above
the capacities of most DSP engineers, unless there's clear professional
guidance and no fear of long and hard work and learning.
Of course you want to return to the director seat after reading this
newsgroup with a good idea of what's realistic, so I suggest strongly
that while it is fun to make Digital Signal Processing work, matching
that enthusiasm has often been found difficult in the sense of great
working results, if you strive for the better things, and may even
have certain secondary goals in mind, like making a consumer-friendly
product, and produces signal which pose no potential hazard to the
hearing, like sudden loud passages, bad resonances, or bad resounding
resonances when played in a reverberant space, it pays to have a good
idea of what is realistic to achieve with the desired allocation of
means.
In fact more than a few of the traditionally known effects were also
used to prevent all too many signal problems when a production would
be put into compressed (like mp3) format, or digitized to a CD. Signal
distortion problems (like interferences with the sample frequency) but
also more advanced signal conditioning, like averaging mid range
frequency components to prevent hearing damage when playing loud, that
must also operate when printed on CD.
Of course there are "virtual atmosphere" effects like simulating a
"live" sound which combine several of the known effect kinds, and can be
complicated to make. It could be you're after that, I don't know.
Of course, there are more than a few "plugins" that people will use to
apply effects to a piece of software, which fit into for instance a VST
slot (on windows machines), that might serve the purpose.
An intelligent mock-up of some Open Source or otherwise freely available
(within the limits of their license) software may be an
intelligent option, either at the small scale, or by using a few
ready-made effects, with a commercial use license (like you make your
changes to the OS software public and accompany the product with the Gnu
Public License),and combining them with well chosen parameters.
Thinking about that the possible application here is to enhance musical
chords playing to learn chords, it may be you have special effects like
harmonizers, chord-enhancing multi-compression, all kinds of filters
including comb filters, and impulse-based and and FFT-based filters in
mind, that's a specialist area, I think, but could be very interesting.
Greetings,
T. Verelst
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