A friend of mine taught a 2 week pronunciation course in Japan last summer and had a lot of success having them do a rap as a final project. You can find a recording (along with student lyrics) here:
http://65.182.169.197/davidfaulhaber/tricky.html
Myself, I've had pretty good success working on sentence level intonation with my students. I'm not sure how it is for Japanese learners, but for Chinese learners of English, the fact that English is a stress-timed language (where stressed syllables are longer) is very tricky. I've been trying to help them with the rhythm, and found it to be pretty useful.
Good luck!
Dave