Few figures have influenced 20th-century music as much as Arnold Schoenberg and Alban Berg. Their letters, one of the most important sources of information about the background to their music, are here published for the first time. The editors have transcribed, translated and annotated more than 800 letters and from this vast body of material have selected 370 that reflect the lives and times of these two great composers. The letters reveal much about the relationship between Berg and Schoenberg: first as pupil and teacher, then as friends and finally, after the premier of Wozzeck, as colleagues and peers. They also shed light on the reasons for Schoenberg's move to Berlin in 1911, the intrigue behind the early demise of the Society for Private Musical Performance, and Schoenberg's feigned indifference to the success of Wozzeck. Schoenberg describes his first years in America and the correspondence ends with Berg's death in 1935. The letters are fully annotated and supplemented with appendices, facsimiles and many photographs.