Interesting read. I'm a lover of cards,I'm a lover of board games, and I'm a lover of music. On the cruises I've been on ,in the Top Sail lounge, I have heard guitars,piano, duets, solos etc. Some good ,some not so much. When my group plays board games we are rarely quiet and lounges may have different meanings to different people. Go to a Royal Caribbean lounge during a Diamond get together and it's loud.
I would find it hard to complain about someone who is enjoying what they too paid for. Maybe it was raining, to windy,to cold outside to play his music.
If it was extremely loud like an electric guitar I may have asked him if he could turn it down a bit but would never ask him to stop playing. I love the guitar and good music.
Just my humble opinion. You probably did the right thing for your options, moving to another location. Top Sail certainly is big enough.