Yes you can but you have to layer the slides on top of each other if that makes any sense.

I have done it and it works beautifully but it is a great deal of work and requires deep concentration.

However, if you plan to use your continuous music Keynote Presentation in iBooks Author, it won’t work. I went to the Apple Store and tried to come up with a workaround but iBooks Author needs to evolve further before we see this feature.