the way in which opera music could be organised on a different basis of organic growth and modulation; and the function of musical motifs in linking elements of the plot whose connections might otherwise be inexplicit. This became known as the leitmotif technique (see below), although Wagner himself did not use this word. However, Wagner relaxed some aspects of his self-imposed restrictions somewhat as the work progressed. As George Bernard Shaw sardonically (and slightly unfairly) noted of the last opera Götterdämmerung: Music Leitmotifs As a significant element in the Ring and his subsequent works, Wagner adopted the use of leitmotifs, which are recurring themes or harmonic progressions. They musically denote an action, object, emotion, character, or other subject mentioned in the text or presented onstage. Wagner referred to them in "Opera and Drama" as "guides-to-feeling", describing how they could be used to inform the listener of a musical or dramatic subtext to the action onstage in the same way as a Greek chorus did for the theatre of ancient Greece. Instrumentation 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. All four parts have a very similar instrumentation. The core ensemble of instruments are one piccolo, three flutes (third doubling second piccolo), three oboes, cor anglais (doubling fourth oboe), three soprano clarinets, one bass clarinet, three bassoons; eight horns (fifth through eight doubling Wagner tubas), three trumpets, one bass trumpet, three tenor trombones, one contrabass trombone (doubling bass trombone), one contrabass tuba; a percussion section with 4 timpani (requiring two players), triangle, cymbals, glockenspiel, tam-tam; six harps and a string section consisting of 16 first and 16 second violins, 12 violas, 12 cellos, and 8 double basses. Das Rheingold requires one bass drum, one