I just loaded up a three year old project in Cubase 9 to find it complaining about missing Groove Agent ONE; I thought that was a bit odd, until I checked and just discovered that it seems to have been removed from Cubase from version 8 onwards.
Sure, we have Groove Agent SE, but that’s no good if you have an old project that used ‘ONE’, and I really do have a problem with unnecessarily removing old plugins from upgrades because really what’s the point? I got burned during the Apple transition to Intel as I used to heavily use the amazing sounding ‘Tonic’ filter a lot in the past only to find out it didn’t survive the transition due to ‘licensing reasons’ and would no longer work since the demise of Rosetta as it’s PowerPC only. This caused me to focus on third party plugins rather than being at Steinberg’s licensing mercy or whims if a built-in plugin I rely on becomes a casualty of upgrading.
In this case fortunately one can simply fish the Groove Agent ONE VST out of the Cubase 7.5 application itself (right click on the actual app -> ‘Show Contents’ -> navigate to VST3) then simply copy the VST into your /Library/Audio/Plugins/VST3 folder and restart C9.