“Silence! The Musical” continues to carve out a commercial Off Broadway life for itself with a transfer to a new midtown venue later this month, when thesp Randy Harrison (“Queer as Folk”) will join the cast.Production has been running downtown for about a year, a notable achievement in an Off Broadway landscape that many commercial producers consider economically inhospitable. Whereas productions such as “Avenue Q” at New World Stages draw auds to Off Broadway thanks to pre-established Broadway cred, the spoofy comedy “Silence!” trades on its unauthorized ties to Oscar-winning thriller “Silence of the Lambs.” The musical initially bowed at the FringeNYC festival in 2005 prior to a London stint. The latest run, toplined by Jenn Harris, opened July 9, 2011. Harrison joins a cast that also includes David Garrison (“Married With Children”). Production will move to the newly opened Elektra Theater, near Times Square, starting July 18. Show will play its final perf at PS 122, its current downtown venue, July 15.