Complex sentence: He also developed the "Wagner bell", enabling the bassoon to reach the low A-natural below the B-flat which is the instrument's lowest note, if such a bell is not to be used, then a contrabassoon should be employed.
Split into simpler sentences: He also developed the "Wagner bell", enabling the bassoon to reach the low A-natural, whereas normally B-flat is the instrument's lowest note. If such a bell is not to be used, then a contrabassoon should be employed.