Pitch Changing

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Pitch changing, or pitch shifting, is closely related to time compression and expansion. Similar algorithms are employed in a different way to achieve pitch changes without altering the length of an audio region.

Digidesign's Pitch Shift plug-in allows you to change the pitch of an audio region up or down by as much as two octaves (plus or minus 24 semi-tones) with or without altering its length. As you can see in Figure 7.16, there is a checkbox for time correction in the Pitch Shift plug-in window that also enables the quality parameters at the bottom of the plug-in window, just like the Time Compression Expansion plug-in.

Figure 7.16. Digidesign's Pitch Shift plug-in.

Pitch shifting is very useful as a sound design tool. All sorts of weird sounds can be made by shifting ordinary sounds outside their normal range. You can pitch change dialog to deepen someone's voice or create imaginary voices for animated characters .

There is a very famous use of pitch shifting in the original Star Wars movie. The Ti Fighter sound was created by hitting a tension wire on a telephone pole and shifting the sound very low. This created the screaming engine effect that was so unique.

If you happen to own Pro Tools HD, you can take advantage of higher sample rates. When pitching down sounds recorded at higher sample rates, ultrasonic harmonics that were inaudible in the original recording will come down into the audible spectrum, creating some very interesting effects. This process was used extensively by sound designer Dane Davis on The Matrix Reloaded . Strange mechanical sounds were created by pitch shifting high-resolution recordings of loud metal clangs to reveal their ultrasonic spectrum.

Try experimenting with any sound you can think of, shifting it up or down. Even subtle pitch changes can help sounds fit into the overall mix of elements in ways that EQ or other processing cannot.

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