Audio Effects – Vocoder and Auto-Tune

Alright, thanks for coming back for my next installment in this article series concerning audio effects. In the past few weeks we have covered quite a few commonly used effects, such as reverb, delay, flange, and compression. These effects all have wide scopes of usage, and are probably used on a daily basis in most modern recording studios, on a wide range of different musical styles. We were discussing the basic functionality of each effect, leaving you to decide if and how you would end up using it in your own production process.

Today we’ll be moving on to a couple of other types of effects, which are probably less used that the others we’ve talked about. Don’t let that fact deter you from reading any further, as these two effects; vocoder and auto-tune, are both very flexible and powerful tools for you to add to your studio arsenal. So, please strap on your learning cap and follow me.

Vocoder

The vocoder (its name being derived from "voice encoder") is a speech analyzer and speech synthesizer. It was originally created for use as a speech coder for the telecommunications industry in the 1930s. It was used for secure radio communication, where voice has to be digitized, encrypted and then transmitted on a narrow, voice-bandwidth channel. The way that the vocoder works is that is finds the basic carrier wave that the human voice produces. This carrier wave is at the fundamental frequency (the lowest frequency in a harmonic series). Is is then measured how its spectral characteristics are changed over time by recording someone speaking. This results in a series of numbers representing these modified frequencies at any particular time as the user speaks. To recreate speech, the vocoder simply reverses the process, creating the fundamental frequency in an oscillator, then passing it through a stage that filters the frequency content based on the originally recorded series of numbers. For musical applications, a source of musical sounds (such as a guitar) is used as the carrier, instead of extracting the fundamental frequency. The vocoder is famous for creating robotic sounding voices, and has been used in film to create; surprisingly, robot voices.

Auto-Tune

Auto-Tune is used for correcting pitch in vocal and instrumental performances. It works by employing digital signal processing algorithms (many which are drawn from the geophysical industry) to continuously detect the pitch of a periodic input signal and changes it to a desired pitch. The harmonization is intended to increase the musical quality of a vocal track without revealing the singing as processed. This works well in a studio environment to correct the performance of vocalists and musicians, after they have recorded their takes. It has also been widely used with extreme parameter values to create a distinct electronic vocal sound.

This wraps up the 5th installment in the DiskFaktory Mastering article series on audio effects. Today we covered a couple of the more fun to work with effects, in my opinion. I myself have learned quite a bit writing today’s article, and I hope you feel the same way. Now we’re much better prepared to create a symphony of robot voices.

About the author:
Jason Cole and DiskFaktory Mastering offer great professional mastering services and information regarding audio engineering and CD mastering in California. Get the professional cd mastering information you are seeking now by clicking here.