SciTech

How Things Work: Auto-tune

You may not know it, but it’s on many of the songs that you hear. It is pretty hard for untrained ears to notice it, but it is very much there. For some artists, it is their claim to fame, while others pretend that they have never used it. Some listeners think that it is the best thing to happen to popular music, while some think it is the worst. Independent of public opinion, few technologies in the last 10 years have changed the music we listen to as much as it has. The technical term for it is pitch correction, but everyone knows it as Auto-Tune.

Auto-Tune is actually a piece of proprietary software made by Antares Software that was first released in 1997, and it has an interesting history. The founder of Antares (Andy Hildebrand) actually worked with Exxon to analyze seismic data for oil prospecting. This involved sending sound waves into the ground and listening for the reflections to determine the location of oil deposits and other regions of interest. Of course, the Earth’s crust is a messy and chaotic place, and making sense of the data required extensive analysis to extract useful information. Hildebrand found that many of the methods to do this could be applied to audio production as well.

What pitch correction software, like Auto-Tune, does is analyze and modify audio signals in a very specific way. According to Riccardo Schulz, associate teaching professor at the school of music here at Carnegie Mellon, pitch correction software is used to “fix up” vocal and other instrumental performances. You input the key and the scale that a song is in to provide a reference frame for the software. When the software receives an audio signal (someone’s voice, for example), it compares the pitch of the signal with the correct pitches for the given key and scale. If the pitch is off, it modifies the signal to move it to the correct pitch (hence pitch correction). It is not perfect, however. If the signal is so far off the mark that the nearest note on the scale is not the note you want, it will still shift to that wrong note, resulting in some awkward sounds. It also works better when the pitch is off by just a little bit, as large shifts tend to introduce noise and weird, artificial-sounding distortion.

It is important to note the difference between pitch shifting and pitch correction. The former involves shifting the frequency of the sound in one direction or the other to change its pitch. It is often done manually and has been around much longer than effective pitch correction software has. It is a highly general term that has many different implementations. Pitch correction is just one such implementation in which the pitch shifting is performed automatically (by the computer) and the shifting is used to reach the target pitch that the recording engineer wants. Schulz notes wryly that pitch correction is used for “recording and live performance, especially for singers who don’t sing in tune.” In recording studios, pitch correction is used to polish tracks and to gloss over any mistakes that the singer may have made. It provides a degree of consistency, which allows recording engineers to work more effectively. And yes, it is used to allow mediocre vocalists to sound “better” than they would. In live shows, it is used extensively to ensure that a sore throat or the stress of an overlong tour doesn’t reduce the quality of the performance. Many artists describe it as a sort of “safety net.”

Schulz also points out that for many genres, such as hip-hip, pop, and rock, “the recording is part of the art.” Many producers and recording engineers take this to heart and use pitch correction as an instrument in itself. The most well-known of such producers is the artist T-Pain. Pitch correction and its more general use for pitch shifting can create new and innovative sonic textures. It can also be used to allow samples that are in different keys or even samples that aren’t musical enough to be used freely.

Many would claim that the use of pitch correction marginalizes the talent of singers by allowing anyone and everyone to belt out a pitch-perfect song. Indeed, we are all so used to hearing perfect voices on songs that we now expect nothing less, and that very expectation ensures that even talented vocalists are compelled to use pitch correction. The truth is that pitch correction cannot salvage truly horrible singers. It assists, rather than overshadows, most singers and allows them to make the songs that we, the listeners, demand.