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6.
Effects Devices
This is the cool stuff; reverbs, phase shifters, delays, chorus', harmonizers...
and combinations never heard before. These devices have come a long way in
20 years. Analog electronics and spring reverbs have given way to very powerful
digital multi-effects units with MIDI capabilities, memory for your favorite
patches and wide dynamic range. Five hundred dollars today, will buy some
awesome sound power that didn't even exist 20 years ago, at any price!
a. Reverb
Reverb units attempt to recreate the sound of a particular space. The way
a "space" sounds is a product of it's size, whether or not it's interior surfaces
are hard and reflective or soft and absorbant, and how these interior surfaces
are arranged. All these factors interact to produce the reverberant sound.
Two spaces can have the same interior volume, but be shaped very differently
and that makes all the difference.
The primary types of spaces are rooms, halls and plates but also can include
chambers, churches, clubs and any number of wild spaces. Some units give you
a few parameters to tweak, others give you pages of possibilities. All start
with at least the "size" of the space. Other tweakable options include the
volume and intensity of "early reflections", the amount of pre-delay to the
reverb, which delays the input send into the reverb and "diffusion" and "depth"
settings which have to do with how intensely the reverb spreads out in the
stereo field.
Special types of "reverse reverbs", where the sound envelope is turned
around and ramps up in volume rather than trailing off, are actually inspired
by the analog trick of "backwards reverb". The important distinction is that
"reverse reverbs" occur after the sound just like regular reverbs. "Backwards
reverb" occurs before the sound and seems to ramp up to the sound.
Backwards effects is an old analog recording technique. The record head
is a fixed alignment of tracks, i.e. 1 - 8. When you turn the tape around
on the tape machine, track 8 becomes 1, track 7 becomes 2, etc. If you record
your stereo backing vocals on tracks 1 and 2, for instance, then, at the end
of the song, turn the tape around and play it back, you will hear those vocals
playing backwards on tracks 7 and 8. Send them to a reverb while you're playing
it backwards and record the reverb on 3 and 4. Think about it; the end of
the sung phrase hits the reverb first and it trails off after the start of
the phrase.
When you turn the tape around and play it forward, the vocals will still
be on 1 and 2, playing correctly, but now there will be "backwards reverb"
ramping up to the start of the sung phrases on track 3 and 4. Check out Pink
Floyd's "Dark Side of the Moon" for some tasty examples of backwards effects.
b. Echoes and Delays
An echo is an acoustic phenomenon where a sound is repeated. The classic
example in mother nature is an echo canyon. Delay units recreate this capability
and give us control of several different parameters. The two most basic are
"delay time", the period between the input and the delayed signal's output,
and "feedback" or "regeneration" as it's sometimes called, which is how many
times the signal repeats as it fades away.
Generally, each successive repeat decreases in volume. When the feedback
control is raised past a certain point, the repeats get louder and louder.
This is called "Runaway Feedback". Some units have a "Infinite Hold" or "Freeze"
feature which captures the input signal and keeps repeating it until you stop
it. To the untrained ear, discrete echoes start to be distinguished at about
20 milli-seconds. Delays lower than this start to sound more like flangers
and chorus effects. Most delay units also give you this capability.
The classic analog delay unit from the 1960's was the Maestro "Echoplex"
and in the 1970's, the Roland "Space Echo". Both used an endless tape loop
and had a fixed record head and movable playback head. You simply moved the
playback head farther from the record head to achieve a longer delay. Early
analog electronic delays began to show up in the 1970's. The fidelity was
somewhat limited and delay times only went to 600 or 700 milli-seconds at
most. Digital delays began to show up in the 1980's and delay times of several
seconds became more common. Modern units offer superb sonics, patch memories
and MIDI implementation.
c. Flanging, Chorus and Phasing
Like "reverse reverbs", these effects were inspired by analog recording
techniques. The famous "slap-back echo" of the 1950's and early 60's was created
by sending the vocal to another tape machine in record and mixing the signal
coming off the repro-head back in with the original. The distance between
the record head and repro-head and the speed of the second machine determined
the time of the "slap-back".
"Flanging" was a variation on this technique. The process starts similarly,
but by rubbing the edge of the flange of the tape reel on the 2nd machine ever so slightly,
the characteristic "Flanging" sound was produced. The time delays involved with
flanging, chorus and phase shifting are usually well below 15 milli-seconds.
Digital delay units simulate these effects by incorporating an oscillator
into their circuitry which allows you to control the speed and depth of the
signal being recombined with the original. Modern devices give you mono and
stereo flanging and chorus effects. Phase Shifters introduce slight time delays
that also change the phase of the signal being recombined. This gives the
distinctive deep sweeping effect that they are known for.
d. Harmonizers and Exciters
Harmonizers are basically like digital delays except they allow us to tune
the pitch of the delays. When slightly detuned and added back in with the
original signal, they are a useful tool for electronically thickening vocals,
guitars, etc. 'Smart' harmonizers are available now that can add designated
pitches according to different musical scales in their internal processors.
The first pitch correction software to
breakthrough big was Antares AutoTune. Originally developed as a plugin for the ProTools recording
format, its now available for most major software recording packages and as a
stand alone hardware unit, the ATR1. It can indeed repair pitch problems in a
performance, but it is now being used as an effect on pop, rap, dance and even country
songs. When it is overdriven, it resembles a vocorder but with more of the human
voice intact.
The famous Aphex "aural exciter" was the first device of it's kind. The
effect is often described as giving "presence" to whatever it's used on. These
kinds of devices all work slightly differently by adding and subtracting harmonics,
or readjusting the balance of phase relationships. It's definitely "voodoo",
but very useful at times.
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