On the full score of the third act (Triumphal Himn) there is an instruction for the copyst: to write the score for the bass clarinet on a separate sheet. Full score contains a supplement where in which Meyerbeer suggests to use a soprano clarinet if no bass clarinet was available. Probably Meyerbeer uses bass clarinet for darkening the tonal colour of the instrumentatio. In the fourth act (Exsorcism) there is bass clarinet solo (from page 8 to page 12)