If you look at the app for the current sailing under music you will see that there are at least 4 scheduled live bands on the pool deck - maybe it’s seasonal
If you look on the app for the current sailing there are a couple of house bands that play around the ship.. think the picture above is what celebrity call their ‘orchestra’ who do the music for the shows
Celebrity don’t really do theme nights . You will have 2 evenings chic nights , possibly a white night and the occasional 30 minute 70/80s ‘show’ in the atrium but people don’t usually dress up in fancy dress’