User Manual

9
How Auto-Tune 7 detects pitch
In order for Auto-Tune 7 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 7 does
exactly this: It looks for a periodically repeating
waveform and calculates the time interval
between repetitions.
The pitch detection algorithm in Auto-Tune
7 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 7 was designed to detect and
correct pitches up to the pitch C6. (If the
input pitch is higher than C6, Auto-Tune 7
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 7 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 7 will not detect pitch
when the input waveform is not periodic. As
demonstrated above, Auto-Tune 7 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 7 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 7 be a bit more casual about what it
considers “periodic.”
Experimenting with this setting will often allow
Auto-Tune 7 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 did a much better
job than any prior version of Auto-Tune with
borderline troublesome material and Auto-Tune
7 does even better yet.
How Auto-Tune 7 corrects pitch
Auto-Tune 7 provides two separate and distinct
ways to approach pitch correction: Automatic
Mode and Graphical Mode. The basic
functionality of each is described below.