I think you'll have to experiment anyway! But I can already say it will help you create frequency related effects, such as controlling the gain depending on the frequency of the signal (kind of frequency-dependent compression), or adjust a cutoff for an instrument depending on the frequency of another, create a ducking delay for high pitches only etc...Same here, although I'm not clear on what I can do with the output automation yet, or what I can actually define as output automation. I'm assuming that will be clearer to me once I play with the official release!
It's also very useful when mixing, to check wether the spectrums of several tracks overlap or not...
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