As Victoria says: for the clients, it’s up to them. When I teach a water aerobics class, I have a selection of ‘lite classics’ with waltzes and marches which is very popular.
As for myself: I am a classical music lover, and my very favorite piece of music is the Triple Concerto by Beethoven. To me, this is one of the most upbeat pieces of music ever written.
I typically play what the client, or group of clients, like. I do not play anything with negative connotations or negative words. It is all kept positive. Even if the song is not extremely upbeat, I have found that if the lyrics are positive, their motivation will increase and help sustain their workout.