Stopping a virtual instrument mid-play?

[BobFrank]

Is it possible to make the sound created by a virtual instrument - including any reverb or delay - stop completely and instantly during a song?

[Acoustica Eric]

The effects (reverb) are a separate thing triggered by the audio being routed through them. If you cut off the audio, the reverb will ring out as normal.
What you can do to achieve this is play your virtual track while recording it on another audio track.
Now you have a wav file/audio object which is a combination of the virtual instrument and any effects you had added to it. Now when you cut it off on the audio track, everything stops, including reverb.