Complex sentence: The band has performed the song with alternative lyrics on numerous occasions, notably when performing on the "Late Show with David Letterman", a chant of "Free Mumia Abu-Jamal" accompanied only by a drumbeat preceded the final chorus.
Split into simpler sentences: The band has performed the song with alternative lyrics on numerous occasions. When performing on the "Late Show with David Letterman", a chant of "Free Mumia Abu-Jamal" accompanied only by a drumbeat preceded the final chorus.