Wagner made significant innovations in orchestration in this work. He wrote for a very large orchestra, using the whole range of instruments used singly or in combination to express the great range of emotion and events of the drama. Wagner even commissioned the production of new instruments, including the Wagner tuba, invented to fill a gap he found between the tone qualities of the horn and the trombone, as well as variations of existing instruments, such as the bass trumpet and a contrabass trombone with a double slide. 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.