I've only been the dueling piano once and that was a while ago. The music is a lot of fun, but I don't remember it being any more adult later in the evening.
Any time there is music (including the live jazz music during the brunch), it's loudest inside the restaurant. I'd roughly divide Brennan's into three area: main room inside, first floor patio and second floor. If you seated in the main room, it would be hard to have a conversation with some with hearing issues when the music is playing. When we've sat on the patio or second floor, you can't really hear the music and the noise level is fine. I like the second floor balcony area the best, but the patio is best for people watching while you eat.
The pork debris was really good. The bread was a toasted ciabatta bread, which was better than the usual English muffin. There was a very generous amount of shredded pork on it. The creole hollandaise was very mild (which is good because some of Brennan's food has quite a quick).
The Bananas Foster French toast was very sweet, so much so that we couldn't finish it (even with everyone at the table taking a taste or two). The bread was soaked in the egg mixture which made the French toast heavier than we like. While it was fun to try, it wasn't something that we order again.