Long version,
Polarity rotation, also sometimes questionably called "phase rotation", is a technique where you rotate the polarity of the waveform, to affect it's symmetry.
By rotating the polarity of an audio file, you can make it perfectly symmetrical. It sounds 99.9% the same, it doesn't affect RMS loudness, but it does affect peak level. When the audio file is in perfect symmetry, it has the lowest digital peak level possible, allowing for maximized loudness.
The reason this is becoming a thing among producers and even in mastering, is because it's a feature in Izotope RX. However, RX is a standalone editor, not a VST. There are a few plugins that allow polarity rotation, but most of them are fake. They use all-pass-filters, that heavily affect the sound. These are creative effects, that can't be used on final stems or mastering free of care.
Real polarity-rotation VSTs do exist, but there's less than 10 of them. The free ones suck (except the one in Reaper). The paid ones cost ~$60.
Now here's the catch:
- most of these plugins don't have a precise peak-meter built in. Melda already has that.
- there is not a single plugin I'm aware of that has M/S processing. Melda already has that.
- you obviously need the code for it. Melda already has that (see below)
Polarity rotation can be done in MFreeformPhase. However, there might be some amount of inaccuracy based on my testing. I assume it's because the plugin is designed like an FFT eq. It's also not simple to use or demonstrate, and you can't type in values.
If you google "phase rotation vst", people are trying to find these plugins, but almost all the suggestions are wrong & don't do what the OP is asking for. Voxengo has a plugin that does it, but it costs $60. While it can rotate both L and R separately, it can't do M/S. Also, you always need to move 2 knobs, and it has a tiny UI.
There's a market for this, and the vacuum hasn't been filled yet. The freebies prove that it's not extremely difficult thing to program, it's just that these freebies are unstable and poorly designed in every other way. Please make it happen.
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To show how polarity rotation can be used on individual sounds, I made this clip. It's a cymbal hitting at exactly -6.00dB (checked with MLoudnessAnalyzer). The first 4 hits are the raw sample. The second 4 hits are the same sample, with polarity adjusted using MFreeformPhase, then volume adjusted to match exact peak volume of -6.00dB.
https://soundcloud.com/dry-cleaning/pol ... al_sharing
The adjusted version is clearly louder, because the original sample had asymmetrical peaks in the middle of the waveform. Adjusting the polarity allowed me to push the gain by roughly 2dB, without clipping or compressing. It works the same way for any audio - kicks, snare, final mixes etc. There's a video (that has been posted before) of a mastering engineer explaining it in RX:
Thank you for reading.
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