You could have downloaded GUidHost 2.4 for Mac from our software library for free. The software is categorized as Audio & Video Tools.
From the developer:
The GUidHost is a Vst instrument host that allows you to load 4 virtual instruments at the time which can be set on 4 different midi channels. This tool can be useful if you have a sequencer that does not support vst instruments such as Protools, DigitalPerformer or the discontinued but still exellent StudioVisionPro.