Antares TASCAM TA-1VP - Manual (Page 8)

8
TASCAM TA-1VP
Really Easy To Use • No scrolling though endless
menus to find the parameter you want. Virtually every
major function is only a single button press away.
Auto-Tune Pitch Correction
In 1997, Antares first introduced the ground-breaking
Auto-Tune Pitch Correcting Plug-In for ProTools™
(eventually followed by most other plug-in formats). Here
was a tool that actually corrected the pitch of vocals and
other solo instruments, in real time, without distortion
or artifacts, while preserving all of the expressive nuance
of the original performance. Recording Magazine called
Auto-Tune a “Holy Grail of recording.” And went on to say,
“Bottom line, Auto-Tune is amazing… Everyone with a
Mac should have this program.”
The TA-1VP's Auto-Tune module is a licensed hardware
implementation of Antare's Auto-Tune Evo pitch
correcting software. Like Auto-Tune, the TA-1VP employs
state-of- the-art digital signal processing algorithms
(many, interestingly enough, drawn from the geophysical
industry) to continuously detect the pitch of a periodic
input signal (typically a solo voice or instrument) and
instantly and seamlessly change it to a desired pitch
(defined by any of a number of user-programmable
scales).
A little bit about pitch
Pitch is typically associated with our perception of
the “highness” or “lowness” of a particular sound. Our
perception of pitch ranges from the very general (the
high pitch of hissing steam, the low pitch of the rumble
of an earthquake) to the very specific (the exact pitch of
a solo singer or violinist). There is, of course, a wide range
of variation in the middle. A symphony orchestra playing
a scale in unison, for example, results in an extremely
complex waveform, yet you are still able to easily sense
the pitch.
The vocalists and the solo instruments that the TA-1VP is
designed to process have a very clearly defined quality
of pitch. The sound-generating mechanism of these
sources is a vibrating element (vocal chords, a string, an
air column, etc.). The sound that is thus generated can
be graphically represented as a waveform (a graph of the
sound’s pressure over time) that is periodic. This means
that each cycle of waveform repeats itself fairly exactly, as
in the periodic waveform shown in the diagram below:
Because of its periodic nature, this sound’s pitch can be
easily identified and processed by the TA-1VP.
Other sounds are more complex. This waveform:
is of a violin section playing a single tone. Our ears
still sense a specific pitch, but the waveform does not
repeat itself. This waveform is a summation of a number
of individually periodic violins. The summation is non-
periodic because the individual violins are slightly out of
tune with respect to one another. Because of this lack of
periodicity, Auto-Tune would not be able to process this
sound.
Some pitch terminology
The pitch of a periodic waveform is defined as the number
of times the periodic element repeats in one second.
This is measured in Hertz (abbreviated Hz.). For example,
the pitch of A3 (the A above middle C on a piano) is
traditionally 440Hz (although that standard varies by a
few Hz. in various parts of the world).
Pitches are often described relative to one another as
intervals, or ratios of frequency. For example, two pitches
are said to be one octave apart if their frequencies differ
by a factor of two. Pitch ratios are measured in units called
cents. There are 1200 cents per octave. For example, two
tones that are 2400 cents apart are two octaves apart. The
traditional twelve- tone Equal Tempered Scale that is used
(or rather approximated) in 99.9% of all Western tonal
music consists of tones that are, by definition, 100 cents
apart. This interval of 100 cents is called a semitone.
How Auto-Tune detects pitch
In order for Auto-Tune to automatically correct pitch, it
must first detect the pitch of the input sound. Calculating
the pitch of a periodic waveform is a straighforward
process. Simply measure the time between repetitions of
the waveform. Divide this time into one, and you have the
frequency in Hertz. The TA-1VP does exactly this: It looks
for a periodically repeating waveform and calculates the
time interval between repetitions.
The pitch detection algorithm in the TA-1VP 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 (no greater
than 4 milliseconds), the output pitch can be detected
and corrected without artifacts in a seamless and
continuous fashion.
The TA-1VP was designed to detect and correct pitches
up to the pitch C6. If the input pitch is higher than C6,
the TA-1VP will often interpret the pitch an octave lower.
This is because it interprets a two cycle repetition as a one
cycle repetition. On the low end, the TA-1VP will detect
pitches as low as 42 Hz. This range of pitches allows
2 – Introducing the TASCAM TA-1VP Vocal Producer