I had to look up how to spell "billiards" and now the search probably things I'm into pool. I'm not - I have never been good at it but have played a few times when I was younger and we knew someone/someplace that had a pool table. I forget how I thought up this excellent pun but I like it a lot. "Acoustic" is kind of the opposite of "electric" when it comes to music - it's very peaceful and also the word sounds like "a cue stick" which is what is used in billiards/pool to hit the balls. But I just looked it up and actually there is the over-arching term "Cue Sports" which is also known as billiards but it includes many games that are played with a cue stick including but not limited to pool. And just thought I'd note that "billiards hall" reminds me of the game Clue where there's a billiards room and that might be where I learned the word "billiards." It's not a common one nowadays.
Text:
A: Why is classical guitar music playing in the billiards hall?
B: It's a-cue-stick!