Is anyone still successfully running Cubase 4.5 on an older Mac OS? If so, which OS?
Since there hasn’t been an answer yet, you might be able to derive an approximate answer from available public resources, like
Since it looks like Cubase 4.5 was released in September 2008, it would seem that MacOS 10.5 Leopard was the then current MacOS.
And since the next release, MacOS 10.6. Snow Leopard was mostly a “performance, efficiency, and stability” release, there’s a decent chance that Cubase 4.5. would work fine (or even better) on it.
It’s less certain to predict/guess if anything newer than 10.6 might still work for Cubase 4.5