Auto LUFS tester for patches.

[Andreya-Autumn]

Context: Discussing the patch library over on the Discord, we're trying to clarify the expectations on loudness in the patch library. It would be good to have a clear loudness target for patch creators, and it would also be good if the factory patches all hit that target.

Tricky thing as always is: human-perceived loudness is only weakly correlated with peak levels.
It would be trivial to automatically adjust all patches to peak at -1db under reasonable playing conditions, but that would result in some patches sounding much louder than others.

LUFS is the closest thing we have to a measurement of actual perceived loudness. In order to avoid doing all this work manually, it'd be useful to make a little tester that takes a MIDI input, plays it with all relevant patches, then outputs a LUFS readout for each patch.

It should be able to do this per category, since mono vs poly, bass vs lead etc etc will require different test MIDI cases.

This will help: https://github.com/klangfreund/LUFSMeter