As a mathematician, I couldn't resist running the probabilities:
If you ride 6 times, you only have a 1.5% chance of hearing all 6 songs.
If you ride 10 times, your chance of getting all 6 songs rises to 27%.
To have a better than 50/50 chance of hearing all 6 songs, you need to ride 13 times, at which your chance rises to 51.4%.
If you ride 20 times, your chances of hearing all 6 rise to 84.8%.
And if you ride 35 times, you get to a 99% chance.
Personally, I've ridden only twice and we got Conga and Disco Inferno.