The .dll file is the VST Plugin
I am doing music production using Image-Line’s Fruity Loops Studio.
Just like all major digital audio workstations (DAW), it is capable of loading DLL files
as plugins called VST plugins (Virtual Studio Technology).
We know DLL files generally contain executable code, and executable code may contain viruses and malware.
I recently asked that question on Information Security Stackexchange.
Does VST have a mechanism not to execute malicious code inside the dll file?
Can I safely install them without anti-virus?
A VST is just a DLL which exposes a specific interface. As such, it can contain arbitrary code, and can do anything that an EXE could do. Treat it as such. If you don’t trust it, don’t run it.
You should carefully research about the VST plugin you are about to install. If the source is not trustworthy enough, don’t install it.
My suggestion anyways, and rather underestimated protip: Disconnect your recording computer from the internet!
That way, your recordings stay safe and your computer is less likely to get hacked or infected by viruses.