Upgrade Manual

Appendix A: "Audio Plugins" 87
Octave Doubling:
Octave doubling is great on instrumental leads, especially
electric guitar or sax. Duplicate a track, then shift the copy by one octave.
An octave down usually works better than an octave up. If you double an
octave up, the pitch shifted track has very noticeable echo-tremolo artifacts,
which may not be desirable.
Artifacts:
In science, the word
artifact
can mean, "Erroneous results caused
by imperfections in the measurement technique." Lens Flare (multiple
reflections in a camera lens) is a good example of a
photographic artifact
.
Similarly,
audio artifacts
are defects introduced by a DSP process.
All pitch shift algorithms introduce artifacts. Different pitch shift designs
create different types of artifacts. The best-sounding pitch shift algorithms
take a long time to process; a tradeoff between speed and quality. To
complicate matters further, some of the best vocal pitch shifters sound
terrible on instruments, and vice-versa.
Large pitch shifts have large artifacts. Polyphonic audio has more artifacts
than monophonic audio.
The Pitch Shifter algorithm used here, is a fast, general duty algorithm. It
sounds good in some applications, and not so good in others. Please don't
expect perfect results. We haven't yet seen any perfect Pitch Shifters.
Auto-Wah
Wah effects were invented in the 60's, pedal-controlled band-pass filters. In
the 70's, 'envelope-follower' boxes became common for electric bass,
clavinet, and guitar.
This Auto-Wah plugin is a classic envelope-follower effect. Loud input
signals increase the filter cutoff frequency, and quiet input signals allow the
filter to "close down." Loud notes become brighter than quiet notes.