What's up with churches and guitars in this joke from The Big Bang Theory?

Question

From The Big Bang Theory S10E12:

Mary: Thank you, God, for the food we are about to receive and for the nourishment of our bodies and bless the hands that prepared it. Amen.

Sheldon: Given that your hands prepared it, isn't that a little self-serving?

Mary: You start changing the words to the prayers, next thing you know, you're in a church with a guitar.

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Not sure if this is to do with Christianity or some TBBT inside joke I'm missing like Sheldon changes words to prayers at home and then later changes words to prayers in church.

Answer 1

Simply put:

• Contemporary worship services stereotypically include both free-form prayers and music accompanied by guitars.
• Traditional worship services stereotypically include the recitation of set prayers, and do not use guitars.

In the joke, Mary makes a slippery-slope argument: that if she diverges from what is "traditional" in one area (changing the words of her set prayer), everything "traditional" is threatened (guitars will be used in worship).

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More fully explained, the joke makes sense when we crudely divide Christian worship services into two groups: liturgical and non-liturgical.

The defining characteristic of liturgical worship services is that the order of events is predefined, or scripted, and improvisation is avoided. But the stereotype of liturgical worship is that it is formal and antiquated. Most relevant to the joke, liturgical worship often includes the recitation of a written prayer. Furthermore, the musical accompaniment in liturgical worship, if there is any at all, is often limited to an organ, piano, or bells, to the exclusion of guitars and drums.

In non-liturgical worship, more improvisation is permitted during the worship service. The minister's prayers are more likely to be extemporaneous (made up on the spot). And in many non-liturgical worship services, different instruments are used, such as guitars.

Historically, the transition away from reciting prayers and toward extemporaneous prayers occurred long ago in many Christian denominations. In many of those churches the more recent transition has been to move away from traditional musical forms (hymns, etc.) and toward contemporary forms, often accompanied by a guitar.

Thus Mary is making a slippery-slope argument: that if she changes the form of her prayer, soon guitars will appear in the worship service.

Of course, the joke relies on a stereotype of liturgical worship – in reality, there are many liturgical worship services where guitars and set prayers coexist. And in at least most liturgical traditions, prayers said at home may be freer and more extemporaneous than those said during the worship service, so Mary wouldn't be doing anything wrong by modifying her prayer.

Answer 2

Worship styles are highly contentious within many churches. Several years ago our music minister died and when we replaced him, his successor started singing more contemporary songs than hymns. Eventually things settled down (with some unwritten rules observed to keep the peace), but there was a long and drawn out internal drama that played out there.

The joke plays on the often bizarre rules people will create as a result of trying to please people who want a more contemporary worship, with modern songs, versus those who want a more traditional worship experience. Often, those rules are raised to the level of being moral or doctrinal rules, and treated with the same gravity. This article by the Babylon Bee (a satirical Christian fake news site, similar to The Onion) makes essentially the same joke that BBT made. Someone broke an unwritten rule and suffered discipline for it

Worship team bassist Kyle Woodward reportedly broke with church tradition Sunday morning by becoming the first known worship bass player in decades to actually utilize the bottom, high G string on his expensive bass guitar, sources confirmed Wednesday.

“The moment just seemed right,” Woodward said after service. “I apologize. Usually I stay within the realm of orthodoxy—after all, if the E and A strings were good enough for the Psalmists, they’re good enough for me.”

While witnesses called the riff a technically sound musical maneuver, many traditionalists were shocked and horrified that the bassist had parted ways with the beloved tradition of simplistic church bass lines.

“We’ve reviewed footage of Woodward’s little stunt up there,” a stern elder Bryce Etherton said in a statement to press. “And while yes, Kyle definitely laid it down like a boss, we’re placing him under our church discipline and restoration process for disregarding the clear regulative guidelines for bass usage in the context of the local church.”

Answer 3

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 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.