into English by Ernest Newman in 1911. Ernst Cassirer, a contemporaneous German philosopher, called it "one of the best interpretations" of Bach. During its preparation Schweitzer became a friend of Cosima Wagner, then resident in Strasbourg, with whom he had many theological and musical conversations, exploring his view of Bach's descriptive music, and playing the major Chorale Preludes for her at the Temple Neuf. Schweitzer's interpretative approach greatly influenced the modern understanding of Bach's music. He became a welcome guest at the Wagners' home, Wahnfried. He also corresponded with composer Clara Faisst, who became a good friend. His pamphlet "The Art of Organ Building and Organ Playing in Germany and France" (1906, republished with an appendix on the state of the organ-building industry in 1927) effectively launched the 20th-century Orgelbewegung, which turned away from romantic extremes and rediscovered baroque principles—although this sweeping reform movement in organ building eventually went further than Schweitzer had intended. In 1909, he addressed the Third Congress of the International Society of Music at Vienna on the subject. Having circulated a questionnaire among players and organ-builders in several European countries, he produced a very considered report. This provided the basis for the International Regulations for Organ Building. He envisaged instruments in which the French late-romantic full-organ sound should work integrally with the English and German romantic reed pipes, and with the classical Alsace Silbermann organ resources and baroque flue pipes, all in registers regulated (by stops) to access distinct voices in fugue or counterpoint capable of combination without loss of distinctness: different voices singing the same music together. Schweitzer also studied piano under Isidor Philipp, head of the piano department at the Paris Conservatory. In 1905, Widor and Schweitzer were among the six musicians who founded the Paris Bach Society, a choir dedicated to performing J. S. Bach's music, for whose concerts Schweitzer took the organ part regularly until 1913. He was also appointed organist for the Bach Concerts of the Orféo Català at Barcelona, Spain, and often travelled there for that purpose. He and Widor collaborated on a new edition of Bach's organ works, with detailed analysis of each work in three languages (English, French, German). Schweitzer, who insisted that the score should show Bach's notation with no additional markings, wrote the commentaries for the Preludes and Fugues, and Widor those for the Sonatas and Concertos: six volumes were published in 1912–14. Three more, to