As a mastering engineer I am asked all the time if a client should have reverb on their master. Like most of the topics I have blogged about, it’s really up to the client and the engineer’s discretion. Sometimes it can be helpful to smooth out transitions between tracks and other times to add a very subtle ambience to a track.
 
Sometimes clients ask me to do an album master with reverb and a radio version without reverb. I read an article by the world-renowned mastering engineer Bob Katz. It describes what I have been telling my clients: “Radio is the great leveler. It will take songs that sound very soft and ‘unpunchy’, and bring them up to compete with the hottest recordings; it will take songs that are extremely hot and processed, and squash them down in a very unpleasant manner. In other words, mastering with over zealous dynamics processing can actually make a record sound bad on the radio, or at least, not as good as properly-prepared competition.” So as a mastering engineer or as a client, just make your track sound like whatever you want it to sound like. Don’t worry about the radio or TV or film or whatever medium it is meant for.
 
John Scrip of Massive Mastering brings up an example of when it can be useful: “Had a recent job come in - Mono, lots of hiss w/pretty obvious gating going on. No chance of remixes or what not. Pulled a lot of hiss out which obviously made it very dull and dark. Added some early reflections and cranked the high end on the reverb and it offered quite a bit of life - and a bit of space as a bonus.” But, and a very BIG but, he continues: “Was it awesome and wonderful? Nope. But it (A) hid a lot of the anomalies that tear away at the "recording magic" (those things that distract from the music by reminding you that "it's just a recording") and (B) made it sound "like it was done that way on purpose" -- Did another one just a couple weeks ago that had really bad clicks and pops going on that really couldn't be rescued. Dug up my old "Vinyl" plug (old Izotope freeware thing) and *added* scratches and clicks and pops and various amounts of mechanical noise. The client absolutely loved it and now it's "artsy" instead of riddled with clicks and pops.”
 
It’s important to know when you want it. Generally speaking, in my very humble opinion, reverb in the mastering world is not necessary. Only in a few unique situations should you turn the reverb knob up.
 
"Wealth is the ability to fully experience life." Henry David Thoreau