Owner`s manual
13
How Auto-Tune Live detects pitch
In order for Auto-Tune Live 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 Live does exactly this: It looks for a
periodically repeating waveform and calculates the time interval between
repetitions.
The pitch detection algorithm in Auto-Tune Live is virtually instantaneous.
It can recognize the repetition in a periodic sound within a few cycles. This
usually occurs before the sound has sucient amplitude to be heard. Used
in combination with an extremely slight processing delay, the output pitch
can be detected and corrected without artifacts in a seamless and continu-
ous fashion.
Auto-Tune Live was designed to detect and correct pitches up to the pitch
C6. (If the input pitch is higher than C6, Auto-Tune Live 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 Live 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 Live will not detect pitch when the input waveform
is not periodic. As demonstrated above, Auto-Tune Live 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 Live will
have diculty 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 Live be a bit more casual about what it considers
“periodic.” Experimenting with this setting will often allow Auto-Tune Live
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 Live (as well as Auto-Tune 7) does even better yet.