Hi. The answer to your question is varied. If you were using version 4 then you need the VST/AU/ReWire add-on to use 3rd party plugins. The plugin needs to be the same as the host. I.e. you need 64 bit plugin installations to work with Studio One. If you have paid for the upgrade to go from v4 to v5 then you do not need the add-on as Artist V5 natively supports Vst etc. Ezdrummer works very well with Studio 1.