Complex sentence: The Jazz Messengers' tour in Japan had ended a few months before this live performance; then the band decided to play two tracks as a homage to Japan: the eponymous "Ugetsu" and "On the Ginza".
Split into simpler sentences: The Jazz Messengers' tour in Japan had ended a few months before this live performance. So, the band decided to play two tracks as a homage to Japan: the eponymous "Ugetsu" and "On the Ginza".