Ableton Forum

Several parameters are not mapable to macros in Convolution Reverb Pro. Decay, Size, Early, Length, Fade In, Fade Out: None of these will map to macros, while everything does.

I think this is because, if you notice, the reverb re-initializes to the new space. Changing those parameters would, in a sense, be like morphing the space in real-time, which I guess is too computationally expensive. Therefore, midi mapping those parameters is useless. You'd just be listening to silence while the plugin remaps to the new settings.

You may be right. That makes sense.

although I think pre-delay should be mappable without artifacts (??