User Manual

11
How Auto-Tune Evo detects pitch
In order for Auto-Tune Evo to automatically
correct pitch, it must first detect the pitch of the
input sound. Calculating the pitch of a periodic
waveform is a straightforward process. Simply
measure the time between repetitions of the
waveform. Divide this time into one, and you
have the frequency in Hertz. Auto-Tune Evo
does exactly this: It looks for a periodically
repeating waveform and calculates the time
interval between repetitions.
The pitch detection algorithm in Auto-Tune
Evo is virtually instantaneous. It can recognize
the repetition in a periodic sound within a few
cycles. This usually occurs before the sound
has sufficient amplitude to be heard. Used in
combination with a slight processing delay, the
output pitch can be detected and corrected
without artifacts in a seamless and continuous
fashion. (Although it must be kept in mind that
some plug-in protocols introduce a certain
amount of inherent and unpredictable delay.)
Auto-Tune Evo was designed to detect and
correct pitches up to the pitch C6. (If the
input pitch is higher than C6, Auto-Tune Evo
will occasionally interpret the pitch an octave
lower. This is because it interprets a two cycle
repetition as a one cycle repetition.) On the
low end, Auto-Tune Evo will detect pitches
as low as 25Hz (when the Bass Input Type
is selected). This range of pitches allows
intonation correction to be performed on
virtually all vocals and instruments.
Of course, Auto-Tune Evo will not detect pitch
when the input waveform is not periodic.
As demonstrated above, Auto-Tune Evo will
fail to tune up even a unison violin section.
But this can also occasionally be a problem
with solo voice and solo instruments as well.
Consider, for example, an exceptionally breathy
voice, or a voice recorded in an unavoidably
noisy environment. The added signal is non-
periodic, and Auto-Tune Evo will have difficulty
determining the pitch of the composite (voice
+ noise) sound. Luckily, there is a control
(the Tracking control, discussed in Chapter
3) that will let Auto-Tune Evo be a bit more
casual about what it considers “periodic.”
Experimenting with this setting will often allow
Auto-Tune Evo to track even noisy signals.
A NOTE: The above description has
been in pretty much every Auto-Tune
manual since the beginning. While it
is still definitely true in the general case, it must
be noted that Auto-Tune Evo will do a much
better job than any prior version of Auto-Tune
with borderline troublesome material.
How Auto-Tune Evo corrects pitch
Auto-Tune Evo provides two separate and
distinct ways to approach pitch correction:
Automatic Mode and Graphical Mode. The
basic functionality of each is described on the
following pages.