I now have a playlist for every length of booking I offer - 15 mins, 30 mins, 45 mins, 1hr, 90 mins, 2hrs.
I use tracks that I like because otherwise I'd be wanting to throw my laptop/phone out the window. Chill out stuff makes me want to puncture my own eardrums.
Apart from the 15 mins, my playlists all have the same "nearly end of booking" track which is the penultimate one. Then the final track is always Latin. Couple are Shakira, one J-Lo, one Mana. I aim for them to be getting showered or dressed during the last one whilst I'm wandering around getting my clothes back on and singing "No pido que todos las dias sean de sol"