How it works
The first 90 seconds yield L/R correlation and mid/side energy. Mid=(L+R)/2 and side=(L-R)/2. Side share is an energy ratio, not a universal width rating.
Worked example
Identical channels give correlation +1 and no side energy. Opposite-polarity channels give -1 and cancel in mono. Listen before changing the mix.
Read the result
Correlation describes the relationship between left and right channels; mid/side energy describes their sum and difference. These measurements are not interchangeable. They can help identify cancellation or a mostly mono source, but they cannot tell you the artistic optimum for a track.
Common mistakes
Do not maximize side energy as a mastering goal. Wide high-frequency ambience and a centered bass can be intentional. A single whole-section correlation value can hide short problems, so listen in mono and inspect the relevant section.
Questions musicians ask
What is stereo width in mastering?
Stereo width describes perceived spread across the stereo field. This tool does not invent one universal width score: it reports correlation and side-energy share, derived from the actual left/right samples.
What is a phase correlation meter?
It compares the channels' relationship. Identical varying channels give +1 correlation; opposite-polarity copies give -1. Silence or a constant signal has no meaningful normalized correlation, so the tool shows an undefined reading rather than a fake zero.
What happens when you convert stereo to mono?
Summing left and right can reduce or cancel opposite-polarity material. With mid=(L+R)/2, exact opposite channels cancel completely. Listen to the mono result before release; a negative reading is a diagnostic clue, not an automatic verdict.
Sources and calculation notes
From measurement to mastering
Understand the measurement, then compare your own mix and reference. Your ears remain the final judge.