Hello, would you like to know how to get Cubase 5 64bit?
You can not buy it anymore officially. But you can run it with a Cubase 9 license.
Sure … I would like Cubase 5 64 bit, because my PC is 64 bits, and also because in the most recent versions of cubase, I can not use the mute function (M) inside the key editor (midi editor).
How to proceed?
Buy Cubase 9.5 and ask the Steinberg support /Mods in here for a Cubase 5 64bit installer download link.
Or if that is no option for you, try to find someone who sells the Cubase 5 version to you.
You can still mute the selected track while using the lower zone key editor. There’s also a preference to automatically select the tracks with highlighted events (which will be the tracks that are open in the key editor).
Do you speak in which Cubase can I do this ??
And how to do ?? 
Cubase Pro 9.5. Just open a MIDI event in the lower zone, and M for mute still works.