families with his precise markings of dynamics and articulation. In the opening phrase, the cellos are supported by wind instruments: When this idea returns towards the end of the prelude, the instrumental colors are varied subtly, with sounds that were new to the 19th century orchestra, such as the cor anglais and the bass clarinet. These, together with the ominous rumbling of the timpani effectively convey the brooding atmosphere: "It’s impressive to see how Wagner… produces balance in his works. He is true genius in this respect, undeniably so, even down to the working out of the exact number of instruments." Boulez is "fascinated by the precision with which Wagner gauges orchestral balance, [which] … contains a multiplicity of details that he achieved with astonishing precision." According to Roger Scruton, "Seldom since Bach's inspired use of obbligato parts in his cantatas have the instruments of the orchestra been so meticulously and lovingly adapted to their expressive role by Wagner in his later operas." Mahler William Austin (1966) says "Mahler expanded the orchestra, going ahead to a historic climax in the direction already marked by Beethoven, Berlioz and Wagner… The purpose of this famous expansion was not a sheer increase in volume, but a greater variety of sound with more nearly continuous gradations… Mahler only occasionally required all his vast orchestra to play together, and his music was as often soft as loud. Its colours were continually shifting, blending or contrasting with each other." Adorno (1971) similarly describes Mahler's symphonic writing as characterised by "massive tutti effects" contrasted with "chamber-music procedures". The following passage from the first movement of his Symphony No. 4 illustrates this: Only in the first bar of the above is there a full ensemble. The remaining bars feature highly differentiated small groups of instruments. Mahler's experienced conductor's ear led him to write detailed performance markings in his scores, including carefully calibrated dynamics. For example, in bar 2 above, the low harp note is marked forte, the clarinets, mezzo-forte and the horns piano. Austin (1966) says that "Mahler cared about the finest nuances of loudness and tempo and worked tirelessly to fix these details in his scores." Mahler's imagination for sonority is exemplified in the closing bars of the slow movement of the Fourth Symphony, where there occurs what Walter Piston (1969, p. 140) describes as "an instance of inspired orchestration… To be noted are the sudden change