This could be a reference to innovative hymn writers Josef Mohr and Franz Gruber who, in the early 19th century, [hastily wrote the Christmas carol *Stille Nacht* for guitar](https://home.snu.edu/~hculbert/silent.htm) in order to rescue the Christmas celebration of an Austrian church whose organ was broken. This hymn was later translated to English as *Silent Night*.

This could also simply be a reference to Contemporary Christian Music (CCM), which is used in a lot of non-traditional Christian services in the USA (and probably elsewhere). CCM relies heavily on secular pop music styles and is often rock guitar-heavy.