When recording music, it is expected that there will be inaccuracies in pitch and rhythm. While it is preferable to fix these issues at the recording stage, there are ways in which these errors can corrected to a degree at the mixing stage. The processes covered here can also be used creatively as well as correctively to result in unique sounds and effects.

Something to bare in mind with pitch and rhythm correction is that the processes involved can introduce artefacts (“unwanted sounds created as a by-product during audio processing") to your recording. These processes should be used to tweak small mistakes rather than major errors. It is always best to re-record a take rather than try and fix the inaccuracy at the mixing stage.

Fixing Pitch Inaccuracies

Fixing Rhythm Inaccuracies

As highlighted in this page on sequencing, MIDI is very easy to manipulate in terms of rhythms and fixing timing issues. It’s not quite so easy with audio files because changing the the length of a waveform affects the pitch.

There are two ways of altering the timing of an audio file; slicing or warping.

Slicing involves your DAW cutting up the audio file into little pieces, based on the peaks or transients in the file. It gets rid of areas where there isn’t any audio and therefore leaves you gaps to move your slices around into to get the timing right. This can also be done manually by cutting up the audio file yourself.

Warping involves extending or shortening an audio file to fit a certain period of time. It can be used in most situations and doesn’t leave you with many artefacts.

You can also use audio quantise but this isn’t recommended because it isn’t always very accurate and can cause more timing issues than it fixes!

Again, an alternative to these methods, if the section concerned is repeated elsewhere in the song, is to replace small errors with material from elsewhere in the song. For instance, if there is a timing issue on a track in a small part of a chorus, this can be replaced with a recording from another chorus in the project.

Parameters for Control and Creativity

All these pitch and rhythm correction methods and technologies can not only be used for corrective purposes but for creative purposes as well. Below are some parameters that can be used for increasing the level of control over the processes and technologies used, and also be used to create unique sounds.

Pitch Parameters

Automatic tuning technology, as well as being used for corrective purposes, is often used creatively to make a sound or voice sound robotic. This is achieved by using the technology to alter the pitch of a sound by a large increment; it takes advantage of the artefacts added when using this process.

Altering the response time of an automatic tuner affects the time it takes for the technology/plugin to respond to a note thats out of tune. A lower response time may reduce the robotic sound. Allows you to have control over the sound that you want.

When using automatic pitch correction technology, you can select the notes and scales used in the piece. Setting the correct scale can help the automatic tuner to pitch the notes correctly.

In most automatic tuning plugins, there is a fine tuning control. This measures in cents and can be very useful in tuning slightly ‘off’ notes. Again, this allows for a high level of control.

Formant shifting does not alter the pitch of a sound but rather alters the timbre, specifically on vocal recordings. Formants are the harmonics present in a voice and defines the timbre of the voice (whether the sound is from the throat or from the diaphragm). This can provide a high level of control when it comes to vocal pitch correction, but can be used creatively as well if applied to instruments and sound sources other than the voice.

Polyphonic re-tuning is technology designed to retune polyphonic sound sources, such as a guitar or piano. Polyphonic means to play “more than one note simultaneously.”

Rhythm Parameters

Time-stretch technology allows you to change the duration of an audio signal without affecting its pitch. This allows for a greater level of control when it comes to correcting rhythm inaccuracies.

When using a slicing plugin, altering the transient detection threshold allows you to have greater control over what the plugin considers a transient ("the peaks in a waveform of an audio recording"), and therefore how many slices are made.

Groove templates allow you to match the ‘groove’ or feel of a audio track with another. By selecting a section of audio from one track and creating a groove template from it, you can then imprint the rhythms from this audio file onto another file. For more detail on how this works, watch the video below.